Skip on-diff getdeps jobs for .llms rule files

Summary:
Add `.llms` directory to `shipit.strip` in the fboss manifest to prevent on-diff getdeps build jobs from running when only Devmate LLM rule files change.

These files are only used for AI-assisted code review and are not needed for OSS builds.

Reviewed By: joseph5wu

Differential Revision: D96996614

fbshipit-source-id: 519115ddb26a8d1eba9e9effe5e2fced295347f0

Author: AarjunC

build/fbcode_builder/manifests/fboss

@@ -64,6 +64,7 @@ fbcode/configerator/structs/neteng/fboss/thrift = configerator/structs/neteng/fb
 ^fbcode/fboss/github/fboss-image/.*
 ^fbcode/fboss/github/.pre-commit-config.yaml
 ^fbcode/fboss/github/requirements-dev.txt
+^fbcode/fboss/.llms/.*
 
 [sandcastle]
 run_tests = off