ui: fix cramped text by reverting line height to 1.2 in HTML renderer

[deanlee]

The previous PR (#36237) cut line_height from 1.2 to 0.9, causing lines to overlap by ~10% and look cramped, hurting readability. Revert to 1.2 to follow standard spacing (1.2–1.5) for clearer text.

Before (Overlapped/Cramped)

After:

[github-actions]

raylib UI Preview

experimental_mode_description : $${\color{red}\text{DIFFERENT}}$$

master	proposed
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openpilot_long_confirmation_dialog : $${\color{red}\text{DIFFERENT}}$$

master	proposed
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settings_software_release_notes : $${\color{red}\text{DIFFERENT}}$$

master	proposed
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All Screenshots