Fix indentation in pull_request.yml

Author: dempseyatgithub

.github/workflows/pull_request.yml

@@ -98,8 +98,8 @@ jobs:
       license_header_check_project_name: "Swift.org"
 
   proposal_validation:
-      name: Proposal Validation
-      uses: ./.github/workflows/proposal_validation.yml
-      with:
-        project: "swift"
-        workflow_test_enabled: true
+    name: Proposal Validation
+    uses: ./.github/workflows/proposal_validation.yml
+    with:
+      project: "swift"
+      workflow_test_enabled: true