Use python-editor-v3-microbit 0.2.0-gray.ramp.63 in the build workflow

The gray-ramp build of the private theme (no gray override, so the
family neutral ramp shows through) — required alongside @microbit/ui
0.0.0-gray.ramp.90: the previous private build still carried the old
branded gray ramp, which merges last and would have overridden the new
base with values the re-pointed call sites no longer expect.

Author: microbit-matt-hillsdon

.github/workflows/build.yml

@@ -40,7 +40,7 @@ jobs:
       - run: npm ci
         env:
           NODE_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      - run: npm install --no-save @microbit-foundation/python-editor-v3-microbit@0.2.0-experiment.rai.62 @microbit-foundation/website-deploy-aws@0.6.0 @microbit-foundation/website-deploy-aws-config@0.9.0 @microbit-foundation/circleci-npm-package-versioner@1
+      - run: npm install --no-save @microbit-foundation/python-editor-v3-microbit@0.2.0-gray.ramp.63 @microbit-foundation/website-deploy-aws@0.6.0 @microbit-foundation/website-deploy-aws-config@0.9.0 @microbit-foundation/circleci-npm-package-versioner@1
         if: github.repository_owner == 'microbit-foundation'
         env:
           NODE_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}