Bump debug, @microsoft/sp-build-web and @microsoft/sp-webpart-workbench

Bumps [debug](https://github.com/debug-js/debug) to 2.6.9 and updates ancestor dependencies [debug](https://github.com/debug-js/debug), [@microsoft/sp-build-web](http://aka.ms/spfx) and [@microsoft/sp-webpart-workbench](http://aka.ms/spfx). These dependencies need to be updated together.


Updates `debug` from 2.2.0 to 2.6.9
- [Release notes](https://github.com/debug-js/debug/releases)
- [Changelog](https://github.com/debug-js/debug/blob/2.6.9/CHANGELOG.md)
- [Commits](https://github.com/debug-js/debug/compare/2.2.0...2.6.9)

Updates `@microsoft/sp-build-web` from 1.10.0 to 1.16.1

Updates `@microsoft/sp-webpart-workbench` from 1.10.0 to 1.12.1

---
updated-dependencies:
- dependency-name: debug
  dependency-type: indirect
- dependency-name: "@microsoft/sp-build-web"
  dependency-type: direct:development
- dependency-name: "@microsoft/sp-webpart-workbench"
  dependency-type: direct:development
...

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

samples/js-theme-manager/package.json

@@ -22,10 +22,10 @@
   },
   "devDependencies": {
     "@microsoft/rush-stack-compiler-3.3": "0.3.5",
-    "@microsoft/sp-build-web": "1.10.0",
+    "@microsoft/sp-build-web": "1.16.1",
     "@microsoft/sp-module-interfaces": "1.10.0",
     "@microsoft/sp-tslint-rules": "1.10.0",
-    "@microsoft/sp-webpart-workbench": "1.10.0",
+    "@microsoft/sp-webpart-workbench": "1.12.1",
     "@types/chai": "3.4.34",
     "@types/mocha": "2.2.38",
     "ajv": "~5.2.2",