chore: Remove the obsolete retrieval service (#543)

This PR also simplifies github workflow configs.

> [!NOTE]
> We would be restoring scripts like `run_generate_embeddings.py`,
`models/`, etc. in #546. In a future PR, we would also reimplementing
data initialization/export scripts using Toolbox

Author: anubhav756

.github/sync-repo-settings.yaml

@@ -29,12 +29,7 @@ branchProtectionRules:
     requiresStrictStatusChecks: true
     requiredStatusCheckContexts:
       - "cla/google"
-      - "retrieval_service"
       - "llm_demo"
-      - "retrieval-service-app-pr (retrieval-app-testing)"
-      - "retrieval-service-postgres-pr (retrieval-app-testing)"
-      - "retrieval-service-alloydb-pr (retrieval-app-testing)"
-      - "retrieval-service-cloudsql-pg-pr (retrieval-app-testing)"
       - "llm-demo-langgraph-pr (retrieval-app-testing)"
 # Set team access
 permissionRules:

.github/workflows/lint.yml

@@ -30,12 +30,8 @@ permissions: read-all
 
 jobs:
   integration:
-    name: ${{ matrix.dir }}
+    name: Cymbal Air
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        dir: [retrieval_service]
-      fail-fast: false
     permissions:
       contents: read
       id-token: write
@@ -51,11 +47,9 @@ jobs:
           python-version: "3.11"
 
       - name: Install requirements
-        working-directory: ${{ matrix.dir }}
         run: pip install -r requirements.txt -r requirements-test.txt
 
       - name: Run lints
-        working-directory: ${{ matrix.dir }}
         run: |
           black --check .
           isort --check .

.github/workflows/lint_fallback.yml

@@ -21,11 +21,8 @@ on:
 
 jobs:
   integration:
-    name: ${{ matrix.dir }}
+    name: Cymbal Air
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        dir: [retrieval_service]
     permissions:
       contents: none