Make contribution.md more readable

[exploratoryprorammer]

Fixed a redundant phrase in the Python setup section ("version of supported Python version").

Corrected the capitalization of macOS.

Fixed a broken document title and punctuation in the ICLA section.

Removed an unopened /div tag at the bottom of the Troubleshooting section

[exploratoryprorammer]

.take-issue

[anowardear062-svg]

Thanks

[Vicky-8223]

I would like to work on it.
.take-issue

[exploratoryprorammer]

.take-issue