ci(actions): we only have one cache key so ditch the newline

Author: jrolfs

.github/workflows/build.yml

@@ -32,8 +32,7 @@ jobs:
         with:
           path: ${{ steps.yarn-cache.outputs.dir }}
           key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-yarn-
+          restore-keys: ${{ runner.os }}-yarn-
 
       - name: Install dependencies
         run: yarn install --frozen-lockfile