CLI: Revert from unconditional .env support

[medikoo]

Internally we decided to not pursue .env loading unconditionally as we were worried to break for users which already use .env files to configure the environment for lambdas, where the same root folder is shared by both service configuration and lambda logic.

This PR is purely about removing the deprecation with which such move was announced

Closes: #8566

[codecov]

Codecov Report

Merging #10003 (9cd7eee) into master (ffbdfed) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #10003      +/-   ##
==========================================
- Coverage   86.17%   86.17%   -0.01%     
==========================================
  Files         330      330              
  Lines       13169    13161       -8     
==========================================
- Hits        11349    11342       -7     
+ Misses       1820     1819       -1     

Impacted Files	Coverage Δ
lib/cli/conditionally-load-dotenv.js	100.00% <ø> (+6.66%)	⬆️
lib/cli/commands-schema/resolve-final.js	91.07% <0.00%> (ø)

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