Changed inconsistent instagram icon color in footer to white

[nehjoshi]

Done

Updated the footer Instagram icon color to white for better accessibility and consistency with surrounding icons. The Vanilla framework doesn't currently support a white Instagram glyph, so I've used a SVG instead as a temporary workaround.

QA

1. Open the webpage and navigate to the section containing social media icons.
2. Confirm that the Instagram icon color is now white (#fff).
3. Check that the icon color matches the surrounding icons for visual consistency.
4. Use a contrast checker to ensure sufficient contrast against the background.
5. Use a screen reader to ensure that the Instagram link is properly announced as "@ubuntudesigners on Instagram."

Issue / Card

I raised this issue a few weeks ago, which can be found here.

Screenshots

[webteam-app]

nehjoshi is not a collaborator of the repo