chore: remove v22 from @types/node check

As of today (13th June 2024), there is no `@types/node@22`. I suspect
this will be added once node v22 is out of `Current` status.

Author: kanej

.github/workflows/hardhat-core-ci.yml

@@ -118,7 +118,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [18, 20, 22]
+        # TODO: Currently there is no @types/node for Node 22,
+        # include it when it is available.
+        node: [18, 20]
     steps:
       - uses: actions/checkout@v4
       - uses: pnpm/action-setup@v2