Docs: update tutorials link to point at new platform section

[getdave]

Description

@WunderBart noticed that the Custom Block Editor tutorial link at

https://github.com/WordPress/gutenberg/blob/master/docs/designers-developers/developers/tutorials/readme.md

...points to the wrong location.

Updates to point at the new Platform section.

How has this been tested?

On branch, verify that the link on the text custom block editor on this page goes to the Custom Block Editor tutorial.

See https://github.com/WordPress/gutenberg/blob/5ceb2eb04c91cc4dd7e36883b172ea41aa452b3f/docs/designers-developers/developers/tutorials/readme.md

Types of changes

Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[github-actions]

Size Change: 0 B

Total Size: 864 kB

ℹ️ View Unchanged

Filename	Size	Change
build/a11y/index.js	1.01 kB	0 B
build/annotations/index.js	3.43 kB	0 B
build/api-fetch/index.js	3.39 kB	0 B
build/autop/index.js	2.58 kB	0 B
build/blob/index.js	620 B	0 B
build/block-directory/index.js	6.02 kB	0 B
build/block-directory/style-rtl.css	760 B	0 B
build/block-directory/style.css	760 B	0 B
build/block-editor/index.js	104 kB	0 B
build/block-editor/style-rtl.css	10.6 kB	0 B
build/block-editor/style.css	10.6 kB	0 B
build/block-library/editor-rtl.css	7.36 kB	0 B
build/block-library/editor.css	7.36 kB	0 B
build/block-library/index.js	115 kB	0 B
build/block-library/style-rtl.css	7.52 kB	0 B
build/block-library/style.css	7.52 kB	0 B
build/block-library/theme-rtl.css	669 B	0 B
build/block-library/theme.css	671 B	0 B
build/block-serialization-default-parser/index.js	1.65 kB	0 B
build/block-serialization-spec-parser/index.js	3.1 kB	0 B
build/blocks/index.js	57.7 kB	0 B
build/components/index.js	191 kB	0 B
build/components/style-rtl.css	15.5 kB	0 B
build/components/style.css	15.5 kB	0 B
build/compose/index.js	5.75 kB	0 B
build/core-data/index.js	10.6 kB	0 B
build/data-controls/index.js	1.03 kB	0 B
build/data/index.js	8.22 kB	0 B
build/date/index.js	5.36 kB	0 B
build/deprecated/index.js	772 B	0 B
build/dom-ready/index.js	569 B	0 B
build/dom/index.js	3.06 kB	0 B
build/edit-post/index.js	91.3 kB	0 B
build/edit-post/style-rtl.css	8.64 kB	0 B
build/edit-post/style.css	8.64 kB	0 B
build/edit-site/index.js	4.64 kB	0 B
build/edit-site/style-rtl.css	2.48 kB	0 B
build/edit-site/style.css	2.48 kB	0 B
build/edit-widgets/index.js	4.44 kB	0 B
build/edit-widgets/style-rtl.css	2.58 kB	0 B
build/edit-widgets/style.css	2.58 kB	0 B
build/editor/editor-styles-rtl.css	381 B	0 B
build/editor/editor-styles.css	382 B	0 B
build/editor/index.js	43.8 kB	0 B
build/editor/style-rtl.css	3.98 kB	0 B
build/editor/style.css	3.97 kB	0 B
build/element/index.js	4.45 kB	0 B
build/escape-html/index.js	734 B	0 B
build/format-library/index.js	7.09 kB	0 B
build/format-library/style-rtl.css	502 B	0 B
build/format-library/style.css	502 B	0 B
build/hooks/index.js	1.92 kB	0 B
build/html-entities/index.js	622 B	0 B
build/i18n/index.js	3.48 kB	0 B
build/is-shallow-equal/index.js	710 B	0 B
build/keyboard-shortcuts/index.js	2.3 kB	0 B
build/keycodes/index.js	1.68 kB	0 B
build/list-reusable-blocks/index.js	2.99 kB	0 B
build/list-reusable-blocks/style-rtl.css	226 B	0 B
build/list-reusable-blocks/style.css	226 B	0 B
build/media-utils/index.js	4.85 kB	0 B
build/notices/index.js	1.57 kB	0 B
build/nux/index.js	3.01 kB	0 B
build/nux/style-rtl.css	616 B	0 B
build/nux/style.css	613 B	0 B
build/plugins/index.js	2.54 kB	0 B
build/primitives/index.js	1.49 kB	0 B
build/priority-queue/index.js	780 B	0 B
build/redux-routine/index.js	2.84 kB	0 B
build/rich-text/index.js	14.3 kB	0 B
build/server-side-render/index.js	2.55 kB	0 B
build/shortcode/index.js	1.7 kB	0 B
build/token-list/index.js	1.27 kB	0 B
build/url/index.js	4 kB	0 B
build/viewport/index.js	1.61 kB	0 B
build/warning/index.js	1.14 kB	0 B
build/wordcount/index.js	1.18 kB	0 B

_{compressed-size-action}

[mkaz]

Good catch, I missed that one 👍