Rename files to preserve history

Test\Eslint fail - this is expected.

Change-Id: I8b47dd48d063aefd96a3c7ce64c6e97273a959d8
diff --git a/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.js b/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts
similarity index 100%
rename from polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.js
rename to polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts