DOC-5616 Support Portal links

[aimurphy]

• Remove the support-url attribute because it isn't used.
• Make it easier to read the supported Python versions for cqlsh, and specify 2.7.12+ because of TLS support.
• Remove two links to a support portal article.
  • Only one was on a published page.
  • The article relates to the standalone cqlsh, and one of the resolutions suggests changing the cqlsh package.
  • Instead, I added the "check TLS support" command to the Astra CLI docs, and mentioned that the user can use venv or symlink as long as the supported Python version is available in the PATH.
  • Preview: cqlsh prerequisites

[plpesvc-ds]

Build successful! ✅
Pull requests with matching branch name doc-5616 included in the build:

• DOC-5616 Support Portal links #34 (this pull request)
• https://github.com/riptano/astra-vector-docs/pull/1341
• https://github.com/riptano/astra-docs/pull/979
• DOC-5616 Support Portal links migration-docs#231
• DOC-5616 Support Portal links streaming-learning-docs#69
• DOC-5616 Support Portal links astra-streaming-docs#161
• https://github.com/riptano/upgrading-docs/pull/53
• https://github.com/riptano/cql-docs/pull/131
• https://github.com/riptano/dev-app-drivers/pull/62

Deploying draft.
Deploy successful! View draft

[eric-schneider]

Suggested change

	The `cqlsh` commands required one of the following supported versions of Python with SSL/TLS:
	The `cqlsh` commands require one of the following supported versions of Python with SSL/TLS:

[eric-schneider]

I'd like @toptobes to review the Python-related changes just to double-check that everything looks right. How the CLI finds a version of Python was something that was discussed in during reviews of the 1.0 overhaul of the docs.