Attempt to limit github action concurrency

Signed-off-by: Steve Coffman <steve@khanacademy.org>

.github/workflows/integration.yml

@@ -1,6 +1,10 @@
 name: Integration
 on: [push, pull_request]
-
+# When a new revision is pushed to a PR, cancel all in-progress CI runs for that
+# PR. See https://docs.github.com/en/actions/using-jobs/using-concurrency
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 jobs:
   integration:
     strategy:

.github/workflows/lint.yml

@@ -1,6 +1,10 @@
 name: Lint
 on: [push, pull_request]
-
+# When a new revision is pushed to a PR, cancel all in-progress CI runs for that
+# PR. See https://docs.github.com/en/actions/using-jobs/using-concurrency
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 jobs:
   lint:
     strategy:

.github/workflows/security.yml

@@ -1,6 +1,10 @@
 name: Security
 on: [push, pull_request]
-
+# When a new revision is pushed to a PR, cancel all in-progress CI runs for that
+# PR. See https://docs.github.com/en/actions/using-jobs/using-concurrency
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 jobs:
   nancy:
     strategy:

.github/workflows/test.yml

@@ -1,6 +1,10 @@
 name: Test
 on: [push, pull_request]
-
+# When a new revision is pushed to a PR, cancel all in-progress CI runs for that
+# PR. See https://docs.github.com/en/actions/using-jobs/using-concurrency
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
 jobs:
   test:
     strategy: