ci: fix dockerfile lint

[sozercan]

What this PR does / why we need it:
fix the dockerfile linter
=> WARN: FromAsCasing: 'as' and 'FROM' keywords' casing do not match

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):
Fixes #

Special notes for your reviewer:

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.23%. Comparing base (3350319) to head (697d64a).
Report is 117 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (3350319) and HEAD (697d64a). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (3350319)	HEAD (697d64a)
unittests	2	1

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3474      +/-   ##
==========================================
- Coverage   54.49%   48.23%   -6.27%     
==========================================
  Files         134      219      +85     
  Lines       12329    14989    +2660     
==========================================
+ Hits         6719     7230     +511     
- Misses       5116     6947    +1831     
- Partials      494      812     +318     

Flag	Coverage Δ
unittests	48.23% <ø> (-6.27%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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

[ritazh]

LGTM