Have wasm job fail the workflow but not block auto-merge

The WebAssembly CI job definition had an unconditional job-level
`continue-on-error` set to `true`, so that it would always report a
successful conclusion, even on failure. This made sense before PR
auto-merge was set up. But these jobs do not typically fail, and
their failures should be more apparent, even if they should not
yet block PRs from being auto-merged.

This commit changes the `wasm` jobs so they are able to fail and
cause the workflow as a whole to have a failing status, while still
not blocking PR auto-merge. `continue-on-error` is removed from the
job definition, but it is also no longer made a dependency of the
required `tests-pass` check.

.github/workflows/ci.yml

@@ -215,8 +215,6 @@ jobs:
 
     runs-on: ubuntu-latest
 
-    continue-on-error: true
-
     strategy:
       matrix:
         target: [ wasm32-unknown-unknown, wasm32-wasi ]
@@ -302,6 +300,7 @@ jobs:
       # List all jobs that are intended NOT to block PR auto-merge here.
       EXPECTED_NONBLOCKING_JOBS: |-
         test-fixtures-windows
+        wasm
         tests-pass
 
     defaults:
@@ -338,7 +337,6 @@ jobs:
       - test-32bit
       - lint
       - cargo-deny
-      - wasm
       - check-packetline
       - check-blocking