remove 12.x EOL release line

.github/workflows/continuous-integration.yml

@@ -11,7 +11,8 @@ jobs:
     strategy:
       matrix:
         operating-system: [ubuntu-latest, macos-latest, windows-latest]
-        node-version: [12.x, 14.x, 16.x, 18.x, 20.x]
+        # Node 12.x is EOL as of April 2022: https://nodejs.org/en/blog/release/v12.13.0.
+        node-version: [14.x, 16.x, 18.x, 20.x]
         # The 'setup-node' action has become unable to locate versions for macos ("darwin") on arm64
         # for some reason. Processor architecture shouldn't affect any of our testing, so we can pin
         # this for now.