Fix example in run command

[rockwotj]

The second stage was missing the number of VU, and actually running that command caused complaints.

[CLAassistant]

All committers have signed the CLA.

[imiric]

Thanks for catching it! This example has been wrong since the beginning of k6 in 2017 😅

[codecov-commenter]

Codecov Report

Merging #3094 (e50d5ef) into master (5738ce0) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head e50d5ef differs from pull request most recent head af5e697. Consider uploading reports for the commit af5e697 to get more accurate results

@@            Coverage Diff             @@
##           master    #3094      +/-   ##
==========================================
- Coverage   75.29%   75.28%   -0.02%     
==========================================
  Files         233      233              
  Lines       17607    17607              
==========================================
- Hits        13258    13255       -3     
- Misses       3497     3500       +3     
  Partials      852      852              

Flag	Coverage Δ
ubuntu	75.28% <100.00%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
cmd/run.go	72.76% <100.00%> (ø)

... and 3 files with indirect coverage changes

[olegbespalov]

Good catch, thanks! 👍