[glean][arm][oss][gh] Use an arm image when using arm runners

Otherwise we would fail trying to set up docker on a bare arm linux
runner

.github/workflows/ci-aarch64.yml

@@ -1,6 +1,6 @@
 # https://docs.github.com/en/free-pro-team@latest/actions/reference/workflow-syntax-for-github-actions
 name: CI-ARM
-on: [push]
+on: [push, pull_request]
 
 env:
   LANG: en_US.UTF-8
@@ -13,9 +13,10 @@ jobs:
       matrix:
         ghc: [8.10.7]
         compiler: [clang]
-    runs-on: 4-core-ubuntu-arm
+
+    runs-on: 2-core-ubuntu-arm
     container:
-      image: ubuntu:22.04
+      image: arm-ubuntu-22
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v4
@@ -41,17 +42,6 @@ jobs:
           echo "MAKEFLAGS=-j$(nproc)" >> "$GITHUB_ENV"
           echo "EXTRA_GHC_OPTS=-j$(nproc) +RTS -A128m -n2m -RTS" >> "$GITHUB_ENV"
 
-      - name: Setup Node
-        uses: actions/setup-node@v4
-        with:
-          node-version: 20
-
-      - name: Install indexer (flow)
-        run: npm install -g flow-bin
-
-      - name: Install indexer (typescript)
-        run: npm install -g @sourcegraph/scip-typescript
-
       - name: Setup Haskell
         run: |
           curl --proto '=https' --tlsv1.2 -sSf "https://downloads.haskell.org/~ghcup/aarch64-linux-ghcup" -o "$LOCAL_BIN"/ghcup