Fix Dark theme icons

[Bikram-ghuku]

Pull Request

Related Issues: [List any related issues or reference them using the syntax #issue_number.]

Fixes #313

Description: 1) Changes to the color of the svg drop down button 2) Changes to the color of the calender icon.

Checklist:

• [x] I have tested my changes.
• [x] My code follows the project's coding standards.
• [x] I have updated the documentation (if applicable).

Screenshots:

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[ani1609]

@Bikram-ghuku good work