Fixes #4615: Increase color contrast ratio between foreground and background in design_menu_item_text

[vrajdesai78]

Explanation

Fixes #4615: Increase color contrast ratio between foreground and background in design_menu_item_text by replacing color_def_oppia_brown_dark to color_def_oppia_red

Essential Checklist

• The PR title and explanation each start with "Fix #bugnum: " (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• Any changes to scripts/assets files have their rationale included in the PR explanation.
• The PR follows the style guide.
• The PR does not contain any unnecessary code changes from Android Studio (reference).
• The PR is made from a branch that's not called "develop" and is up-to-date with "develop".
• The PR is assigned to the appropriate reviewers (reference).

Before

After

[rt4914]

LGTM, Thanks.