flow: Remove all suppress_comments.

Now, we're not erasing any of the default suppression comments, and
we're not adding our own. So at this point we're relying on exactly
the default set of suppression comments. This is a requirement as of
Flow v0.127. [1]

Follows the template-app change in facebook/react-native@afad239d7,
on the path to the RN v0.64 upgrade.

[1] https://flow.org/en/docs/config/options/#toc-suppress-comment-regex

.flowconfig

@@ -122,9 +122,5 @@ module.file_ext=.js
 module.file_ext=.json
 module.file_ext=.ios.js
 
-suppress_comment=\\(.\\|\n\\)*\\$FlowFixMe\\($\\|[^(]\\|(\\(<VERSION>\\)? *\\(site=[a-z,_]*react_native\\(_ios\\)?_\\(oss\\|fb\\)[a-z,_]*\\)?)\\)
-suppress_comment=\\(.\\|\n\\)*\\$FlowIssue\\((\\(<VERSION>\\)? *\\(site=[a-z,_]*react_native\\(_ios\\)?_\\(oss\\|fb\\)[a-z,_]*\\)?)\\)?:? #[0-9]+
-suppress_comment=\\(.\\|\n\\)*\\$FlowExpectedError
-
 [version]
 ^0.125.0