chore(cli): update cdk flags message

[kaizencc]

even though it works, the option should come after the command name.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.78%. Comparing base (6f4e98a) to head (95a65ea).
⚠️ Report is 37 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/aws-cdk/lib/cli/cdk-toolkit.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #831      +/-   ##
==========================================
- Coverage   82.82%   81.78%   -1.05%     
==========================================
  Files          65       65              
  Lines        9509     9509              
  Branches     1119     1096      -23     
==========================================
- Hits         7876     7777      -99     
- Misses       1599     1701     +102     
+ Partials       34       31       -3     

Flag	Coverage Δ
suite.unit	81.78% <0.00%> (-1.05%)	⬇️

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