Rename files to preserve history

Test\Eslint fail - this is expected.

Change-Id: I2360e8b9f71b36aefdd3879abba5861f7c099efc
diff --git a/polygerrit-ui/app/elements/shared/gr-tooltip/gr-tooltip.js b/polygerrit-ui/app/elements/shared/gr-tooltip/gr-tooltip.ts
similarity index 100%
rename from polygerrit-ui/app/elements/shared/gr-tooltip/gr-tooltip.js
rename to polygerrit-ui/app/elements/shared/gr-tooltip/gr-tooltip.ts