fix(ci): drop Node 14 from unit test matrix

Node 14 ships with npm 6, which does not support workspaces.
The build step requires workspace symlinks to resolve internal
packages, so unit tests cannot run on Node 14.

Node 14 runtime compatibility is already verified by the
end-to-end tests, which build on Node 22 and run on Node 14.

Author: oetr

.github/workflows/run-all-tests-pr.yaml

@@ -41,9 +41,8 @@ jobs:
         os: [windows-latest, ubuntu-latest, macos-latest]
         node: [20]
         include:
-          # Floor: legacy compatibility check
-          - os: ubuntu-latest
-            node: 14
+          # Node 14 runtime compatibility is covered by end-to-end tests.
+          # Unit tests require npm 7+ (workspaces) which Node 14 doesn't ship.
           # Ceiling: current LTS
           - os: ubuntu-latest
             node: 24