[BUG] Unicode in pull title causes unnecessary change event on PATCH

Hi,

I think this is a bug. Apologies if I’m mistaken.
This bug was discovered after investigating this issue. I’ve now managed to reproduce the bug just using curl against the API.

This first pair of requests creates and updates a pull without any unicode in the title. As the PATCH request contains a title that is identical to the existing title, this results in no change notification, which is the expected result. By “change notification” what I’m referring to is the line that appears in the pull request saying something like “peter-evans changed the title foo bar 2 minutes ago.”

curl \
  -X POST \
  -i \
  -H "Authorization: token <redacted>" \
  -H "Accept: application/vnd.github.v3+json" \
  https://api.github.com/repos/peter-evans/actions-playground/pulls \
  -d '{"head":"feature-1","base":"master","title":"title"}'
HTTP/1.1 201 Created
curl \
  -X PATCH \
  -i \
  -H "Authorization: token <redacted>" \
  -H "Accept: application/vnd.github.v3+json" \
  https://api.github.com/repos/peter-evans/actions-playground/pulls/341 \
  -d '{"title":"title"}'
HTTP/1.1 200 OK

Now if we execute the same pair of requests with a unicode character in the title, it creates a change notification despite the fact that the title is identical in the PATCH request.

curl \
 -X POST \
 -i \
 -H "Authorization: token <redacted>" \
 -H "Accept: application/vnd.github.v3+json" \
 https://api.github.com/repos/peter-evans/actions-playground/pulls \
 -d '{"head":"feature-1","base":"master","title":"title→test"}'
HTTP/1.1 201 Created
curl \
  -X PATCH \
  -i \
  -H "Authorization: token <redacted>" \
  -H "Accept: application/vnd.github.v3+json" \
  https://api.github.com/repos/peter-evans/actions-playground/pulls/342 \
  -d '{"title":"title→test"}'
HTTP/1.1 200 OK

This results in the following unnecessary change notification in the pull request. This is inconsistent behaviour and causes a problem for automated tooling that expects PATCH requests with identical content to complete silently if there are no changes.