test: ci tests on node 22 rather than 21 (#2322)

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> Most PRs should close a specific Issue. All PRs should at least
reference one or more Issues. Edit and/or delete the following lines as
appropriate (note: you don't need both `refs` and `closes` for the same
one):

Closes: #2314 
Refs: #2231
b11beba

## Description

Now that nvm recognizes Node 22, we should probably redo the change from
#2231 undone by
b11beba
.

### Security Considerations

Whether our code works on Node 22 is much more relevant, including for
security, than whether it works on Node 21. Indeed, until 22 could be
used we were using Node 21 only for early warning about Node 22.

### Scaling Considerations

none
### Documentation Considerations

none
### Testing Considerations

the point. Now that Node 22 is out, we should test on it.
### Compatibility Considerations

Hopefully none
### Upgrade Considerations

None

.github/workflows/ci.yml

@@ -70,7 +70,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [18.x, 20.x, 21.x]
+        node-version: [18.x, 20.x, 22.x]
         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