Remove useless whitespace in Websocket output (backport #9720)

[mergify]

This is an automatic backport of pull request #9720 done by Mergify.
Cherry-pick of 20ffa4f has failed:

On branch mergify/bp/v0.37.x/pr-9720
Your branch is up to date with 'origin/v0.37.x'.

You are currently cherry-picking commit 20ffa4fd3.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   rpc/jsonrpc/server/http_server.go
	modified:   rpc/jsonrpc/server/ws_handler.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG_PENDING.md
	both modified:   rpc/jsonrpc/server/http_server_test.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[thanethomson]

@Mergifyio backport mergify/bp/v0.37.x/pr-9650

[mergify]

backport mergify/bp/v0.37.x/pr-9650

🟠 Waiting for conditions to match

• merged [:pushpin: backport requirement]

[thanethomson]

@Mergifyio rebase v0.37.x

[mergify]

rebase v0.37.x

✅ Nothing to do for rebase action

[thanethomson]

This PR should be rebased after we merge #9665. That should fix the conflicts.