Bump diff from 4.0.2 to 4.0.4 in /webapp

Bumps [diff](https://github.com/kpdecker/jsdiff) from 4.0.2 to 4.0.4.
- [Changelog](https://github.com/kpdecker/jsdiff/blob/master/release-notes.md)
- [Commits](kpdecker/jsdiff@v4.0.2...v4.0.4)

---
updated-dependencies:
- dependency-name: diff
  dependency-version: 4.0.4
  dependency-type: indirect
...

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

Author: dependabot[bot]

webapp/yarn.lock

@@ -4680,9 +4680,9 @@ detect-port-alt@^1.1.6:
     debug "^2.6.0"
 
 diff@^4.0.1:
-  version "4.0.2"
-  resolved "https://registry.yarnpkg.com/diff/-/diff-4.0.2.tgz#60f3aecb89d5fae520c11aa19efc2bb982aade7d"
-  integrity sha512-58lmxKSA4BNyLz+HHMUzlOEpg09FV+ev6ZMe3vJihgdxzgcwZ8VoEEPmALCZG9LmqfVoNMMKpttIYTVG6uDY7A==
+  version "4.0.4"
+  resolved "https://registry.yarnpkg.com/diff/-/diff-4.0.4.tgz#7a6dbfda325f25f07517e9b518f897c08332e07d"
+  integrity sha512-X07nttJQkwkfKfvTPG/KSnE2OMdcUCao6+eXF3wmnIQRn2aPAHH3VxDbDOdegkd6JbPsXqShpvEOHfAT+nCNwQ==
 
 dir-glob@^3.0.1:
   version "3.0.1"