docs(install): use material admonition instead of unicode caution

[agilgur5]

Motivation

• use admonitions that come with the material theme instead of a unicode caution sign
  • consistent with the design of the docs

Modifications

• replace unicode caution signs with admonitions

• be more specific in the notes as well

  • using a remote base is not inherently "dangerous" as the previous sentence said without elaboration
    • instead specify that you should use a full hash when using a remote base
    • and add a link to Kustomize's remote base docs
  • similarly in the second note, specify what "tip" means
    • and specify what you should do instead of using latest

Verification

1. mkdocs build passes
2. Looks as expected:

   • Before:
     

   • After:
     

[agilgur5]

Backported cleanly to release-3.5 as 0d4bb58