Bump ajv from 5.2.5 to 6.12.3 in /TeamTabs/spfx-teams-manual-manifest

Bumps [ajv](https://github.com/ajv-validator/ajv) from 5.2.5 to 6.12.3.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v5.2.5...v6.12.3)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: direct:development
...

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

Author: dependabot[bot]

TeamTabs/spfx-teams-manual-manifest/package-lock.json

@@ -36,6 +36,6 @@
     "gulp": "~3.9.1",
     "@types/chai": "3.4.34",
     "@types/mocha": "2.2.38",
-    "ajv": "~5.2.2"
+    "ajv": "~6.12.3"
   }
 }