Remove @nocollapse annotation which was closure-specific.

[samouri]

summary
The @nocollapse property allows for exporting mutable props, but is a Closure-specific annotation.

We no longer need this annotation now that we don't use Closure.

[amp-owners-bot]

Hey @gmajoulet! These files were changed:

extensions/amp-story-dev-tools/0.1/amp-story-dev-tools-tab-debug.js
extensions/amp-story-page-attachment/0.1/amp-story-draggable-drawer.js
extensions/amp-story-player/0.1/amp-story-player.js
extensions/amp-story/1.0/amp-story-grid-layer.js
extensions/amp-story/1.0/amp-story-page.js
extensions/amp-story/1.0/amp-story.js

Hey @mszylkowski! These files were changed:

extensions/amp-story-dev-tools/0.1/amp-story-dev-tools-tab-debug.js
extensions/amp-story-page-attachment/0.1/amp-story-draggable-drawer.js

Hey @newmuis! These files were changed:

extensions/amp-story-page-attachment/0.1/amp-story-draggable-drawer.js
extensions/amp-story-player/0.1/amp-story-player.js
extensions/amp-story/1.0/amp-story-grid-layer.js
extensions/amp-story/1.0/amp-story-page.js
extensions/amp-story/1.0/amp-story.js

Hey @alanorozco! These files were changed:

extensions/amp-story-player/0.1/amp-story-player.js