Code block: fix direction for RTL languages

[sabernhardt]

Description

Issue reported by @farhadsakhaei (farhad0) in Trac 62170

Contents of the Code block should display in LTR direction, but RTL sites do not ensure that. This can be seen in a support topic from the WordPress.org forums.

Step-by-step reproduction instructions

1. Set your site language to a right-to-left language (and set your profile language to match the site).
2. Go to the post editor.
3. Add a Code block and insert some code.
4. Save changes.
5. View the direction and alignment both in the editor and on the front.

Screenshots, screen recording, code snippet

From the support topic:

Using the same code snippet in Twenty Twenty-Four, with WordPress trunk and Gutenberg 19.3.0:

Environment info

• WordPress 6.7-trunk, with and without Gutenberg 19.3.0
• Twenty Twenty-Four
• Firefox 131.0 with Windows 10

Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes