Remove whitespace from textarea PDF settings

[jakejackson1]

Description

The new-lines and tabs between the opening and closing <textarea> tags were causing display problems in the PDF settings.

Testing instructions

1. Activate Core Booster 2.1 and view the Additional CSS section

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

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (924f210) 75.13% compared to head (e6ca498) 75.14%.

Files	Patch %	Lines
src/Helper/Helper_Abstract_Options.php	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #1493 +/- ## ================================================= + Coverage 75.13% 75.14% +0.01% Complexity 2953 2953 ================================================= Files 243 243 Lines 12883 12881 -2 Branches 370 370 ================================================= Hits 9679 9679 + Misses 3196 3194 -2 Partials 8 8 ```

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