Bump tinymce-rails from 6.3.1 to 8.1.2

Bumps [tinymce-rails](https://github.com/spohlenz/tinymce-rails) from 6.3.1 to 8.1.2.
- [Release notes](https://github.com/spohlenz/tinymce-rails/releases)
- [Commits](spohlenz/tinymce-rails@v6.3.1...v8.1.2)

---
updated-dependencies:
- dependency-name: tinymce-rails
  dependency-version: 8.1.2
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -541,7 +541,7 @@ GEM
     tilt (2.6.0)
     timecop (0.9.10)
     timeout (0.4.3)
-    tinymce-rails (6.3.1)
+    tinymce-rails (8.1.2)
       railties (>= 3.1.1)
     typhoeus (1.4.1)
       ethon (>= 0.9.0)