Remove rotation from Transformation demo description since it's not implemented (#968)

## Description

The transformation demo does not include rotation, but the description
and subtitle says it does. This PR removes mention of rotation.

Rotation is not currently supported by InteractiveViewer under the hood,
though someday I'd like it to!

@guidezpl What's the process for updating an existing string like this?
I couldn't figure it out by reading the [l10n
readme](https://github.com/flutter/gallery/tree/main/lib/l10n#readme).

## Tests

None.

## Issues
Fixes #967

---------

Co-authored-by: Pierre-Louis <6655696+guidezpl@users.noreply.github.com>

Author: justinmc

lib/l10n/README.md

@@ -56,3 +56,8 @@ console to generate messages in the different locales.
 > unless necessary.
 
 See `/third_party/dart/flutter_gallery/README.md` for how to import this file and export translations.
+
+## Updating Existing Locale Messages
+
+Modify the message in `intl_en.arb`, then run `flutter pub run grinder l10n`.
+This will update `intl_en_US.xml` for the translation console.

lib/l10n/intl_en.arb

@@ -1787,11 +1787,11 @@
   "@demo2dTransformationsTitle": {
     "description": "Title for the 2D transformations demo."
   },
-  "demo2dTransformationsSubtitle": "Pan, zoom, rotate",
+  "demo2dTransformationsSubtitle": "Pan and zoom",
   "@demo2dTransformationsSubtitle": {
     "description": "Subtitle for the 2D transformations demo."
   },
-  "demo2dTransformationsDescription": "Tap to edit tiles, and use gestures to move around the scene. Drag to pan, pinch to zoom, rotate with two fingers. Press the reset button to return to the starting orientation.",
+  "demo2dTransformationsDescription": "Tap to edit tiles, and use gestures to move around the scene. Drag to pan and pinch with two fingers to zoom. Press the reset button to return to the starting orientation.",
   "@demo2dTransformationsDescription": {
     "description": "Description for the 2D transformations demo."
   },

lib/l10n/intl_en_US.xml

@@ -1680,11 +1680,11 @@
   <string
     name="demo2dTransformationsSubtitle"
     description="Subtitle for the 2D transformations demo."
-    >Pan, zoom, rotate</string>
+    >Pan and zoom</string>
   <string
     name="demo2dTransformationsDescription"
     description="Description for the 2D transformations demo."
-    >Tap to edit tiles, and use gestures to move around the scene. Drag to pan, pinch to zoom, rotate with two fingers. Press the reset button to return to the starting orientation.</string>
+    >Tap to edit tiles, and use gestures to move around the scene. Drag to pan and pinch with two fingers to zoom. Press the reset button to return to the starting orientation.</string>
   <string
     name="demo2dTransformationsResetTooltip"
     description="Tooltip for a button to reset the transformations (scale, translation) for the 2D transformations demo."