Bump tar and canvas

Removes [tar](https://github.com/isaacs/node-tar). It's no longer used after updating ancestor dependency [canvas](https://github.com/Automattic/node-canvas). These dependencies need to be updated together.


Removes `tar`

Updates `canvas` from 2.11.2 to 3.2.1
- [Release notes](https://github.com/Automattic/node-canvas/releases)
- [Changelog](https://github.com/Automattic/node-canvas/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Automattic/node-canvas/compare/v2.11.2...v3.2.1)

---
updated-dependencies:
- dependency-name: tar
  dependency-version: 
  dependency-type: indirect
- dependency-name: canvas
  dependency-version: 3.2.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -51,7 +51,7 @@
     "allotment": "1.20.2",
     "applicationinsights": "1.8.0",
     "bootstrap": "3.4.1",
-    "canvas": "2.11.2",
+    "canvas": "3.2.1",
     "clean-webpack-plugin": "4.0.0",
     "clipboard-copy": "4.0.1",
     "copy-webpack-plugin": "11.0.0",