Minor fixes to Dockerfile and docs

[shubham-pampattiwar]

Please add a summary of your change

Fixes build warnings like FromAsCasing: 'as' and 'FROM' keywords' casing do not match

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.77%. Comparing base (dd3d05b) to head (3aabfc3).
Report is 24 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8108      +/-   ##
==========================================
- Coverage   58.77%   58.77%   -0.01%     
==========================================
  Files         358      358              
  Lines       30070    30084      +14     
==========================================
+ Hits        17674    17682       +8     
- Misses      10949    10954       +5     
- Partials     1447     1448       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[kaovilai]

Specifically: https://docs.docker.com/reference/build-checks/from-as-casing/