Better compatibility with Weglot

[jakejackson1]

Description

The Weglot plugin includes a feature that auto-injects the language selector. This was running when the PDF is viewed/downloaded, and could corrupt the documents.

Testing instructions

I wasn't able to replicate the problem on a fresh development site, and it was only present on a customer's site. I'm unsure of the exact combination of variables that triggers this bug, but tested the fix on the customers website.

Screenshots

Checklist:

• [x] I've tested the code.
• [ ] My code is easy to read, follow, and understand
• [ ] My code follows the accessibility standards.
• [ ] My code has proper inline documentation / docblocks.

Additional Comments

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 76.98%. Comparing base (a4f089f) to head (155b8bd).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #1505 +/- ## ============================================ Coverage 76.97% 76.98% ============================================ Files 244 244 Lines 12741 12744 +3 Branches 370 370 ============================================ + Hits 9808 9811 +3 Misses 2925 2925 Partials 8 8 ```

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