test: Drop Windows CI (#2240)

We’ve seen a lot of EPIPE on write failures that are more common on
Windows than Linux/Mac, though they do occur. For that reason along, it
would be good to restore Windows CI when we track that issue down, but
for now, the flakes are too hard to bear and also block us from
upgrading yarn #2222

Tracking revert #2243

.github/workflows/ci.yml

@@ -78,7 +78,10 @@ jobs:
       fail-fast: false
       matrix:
         node-version: [18.x, 20.x, 21.x]
-        platform: [ubuntu-latest, windows-latest]
+        platform: [ubuntu-latest]
+        # windows-latest exhibited flakey tests that are not yet worth the
+        # trouble to investigate, and blocked us from upgrading yarn from 1 to
+        # 4.
 
     steps:
       - name: Checkout