Bump immutable from 5.1.2 to 5.1.5 in /welcome

Bumps [immutable](https://github.com/immutable-js/immutable-js) from 5.1.2 to 5.1.5.
- [Release notes](https://github.com/immutable-js/immutable-js/releases)
- [Changelog](https://github.com/immutable-js/immutable-js/blob/main/CHANGELOG.md)
- [Commits](immutable-js/immutable-js@v5.1.2...v5.1.5)

---
updated-dependencies:
- dependency-name: immutable
  dependency-version: 5.1.5
  dependency-type: indirect
...

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

Author: dependabot[bot]

welcome/yarn.lock

@@ -2338,9 +2338,9 @@ ignore@^5.2.0:
   integrity sha512-hsBTNUqQTDwkWtcdYI2i06Y/nUBEsNEDJKjWdigLvegy8kDuJAS8uRlpkkcQpyEXL0Z/pjDy5HBmMjRCJ2gq+g==
 
 immutable@^5.0.2:
-  version "5.1.2"
-  resolved "https://registry.yarnpkg.com/immutable/-/immutable-5.1.2.tgz#e8169476414505e5a4fa650107b65e1227d16d4b"
-  integrity sha512-qHKXW1q6liAk1Oys6umoaZbDRqjcjgSrbnrifHsfsttza7zcvRAsL7mMV6xWcyhwQy7Xj5v4hhbr6b+iDYwlmQ==
+  version "5.1.5"
+  resolved "https://registry.yarnpkg.com/immutable/-/immutable-5.1.5.tgz#93ee4db5c2a9ab42a4a783069f3c5d8847d40165"
+  integrity sha512-t7xcm2siw+hlUM68I+UEOK+z84RzmN59as9DZ7P1l0994DKUWV7UXBMQZVxaoMSRQ+PBZbHCOoBt7a2wxOMt+A==
 
 import-fresh@^3.2.1, import-fresh@^3.3.0:
   version "3.3.1"