build: bump azure-identity in /ResearchAssistant/App

Bumps [azure-identity](https://github.com/Azure/azure-sdk-for-python) from 1.14.0 to 1.19.0.
- [Release notes](https://github.com/Azure/azure-sdk-for-python/releases)
- [Changelog](https://github.com/Azure/azure-sdk-for-python/blob/main/doc/esrp_release.md)
- [Commits](Azure/azure-sdk-for-python@azure-identity_1.14.0...azure-identity_1.19.0)

---
updated-dependencies:
- dependency-name: azure-identity
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

ResearchAssistant/App/requirements.txt

@@ -1,4 +1,4 @@
-azure-identity==1.14.0
+azure-identity==1.19.0
 Flask==3.0.0
 openai==1.58.1
 azure-search-documents==11.4.0b6