Bump jest from 25.3.0 to 26.6.3 in /webapp

Bumps [jest](https://github.com/facebook/jest) from 25.3.0 to 26.6.3.
- [Release notes](https://github.com/facebook/jest/releases)
- [Changelog](https://github.com/facebook/jest/blob/master/CHANGELOG.md)
- [Commits](jestjs/jest@v25.3.0...v26.6.3)

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

webapp/package.json

@@ -131,7 +131,7 @@
     "faker": "^4.1.0",
     "flush-promises": "^1.0.2",
     "identity-obj-proxy": "^3.0.0",
-    "jest": "~25.3.0",
+    "jest": "~26.6.3",
     "mutation-observer": "^1.0.3",
     "node-sass": "~4.13.1",
     "prettier": "~2.2.1",