adds reviewer feedback

Signed-off-by: Hanan Younes <hanan.algazaley@gmail.com>

content/docs/for-buildpack-authors/how-to/write-buildpacks/create-slice-layers.md

@@ -7,7 +7,7 @@ A `Slice` represents a layer in the `<app>` directory to be exported during the
 
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-A buildpack MAY specify sub-paths within `<app>` as `slices` in `launch.toml`. Separate layers MUST be created during the [export](https://buildpacks.io/docs/for-buildpack-authors/concepts/lifecycle-phases/#phase-5-export) phase for each slice with one or more files or directories.
+A buildpack may specify sub-paths within `<app>` as `slices` in `launch.toml`. The lifecycle will create separate layers during the [export](https://buildpacks.io/docs/for-buildpack-authors/concepts/lifecycle-phases/#phase-5-export) phase for each slice with one or more files or directories.
 
 ## Key Points