fix(guided remediation): remove --relock-cmd flag

[michaelkedar]

--relock-cmd let you override the npm install command with an arbitrary command to regenerate the package-lock.json after doing a relax.
We probably don't want to have that option in osv-scalibr when we migrate this there, so I've removed it now before the v2 release of osv-scanner.

If someone actually needs this, they can run the command themselves outside of osv-scanner.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 69.00%. Comparing base (33c8a7a) to head (a3f9b48).

Files with missing lines	Patch %	Lines
cmd/osv-scanner/fix/state-relock-result.go	0.00%	2 Missing ⚠️
cmd/osv-scanner/fix/noninteractive.go	0.00%	0 Missing and 1 partial ⚠️
cmd/osv-scanner/fix/regen_lockfile.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1517      +/-   ##
==========================================
+ Coverage   68.98%   69.00%   +0.01%     
==========================================
  Files         197      197              
  Lines       18800    18791       -9     
==========================================
- Hits        12970    12966       -4     
+ Misses       5127     5121       -6     
- Partials      703      704       +1     

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