docs: update contribution documentation

[drexler]

Which problem is this PR solving?

• [Docs] The getting started docs for running lint is incorrect #1834

Short description of the changes

• Corrects NPM script commands in the contributing guide

[codecov]

Codecov Report

Merging #1858 (24f338d) into master (960b868) will increase coverage by 0.23%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1858      +/-   ##
==========================================
+ Coverage   92.39%   92.63%   +0.23%     
==========================================
  Files         170      174       +4     
  Lines        5733     6054     +321     
  Branches     1235     1288      +53     
==========================================
+ Hits         5297     5608     +311     
- Misses        436      446      +10     

Impacted Files	Coverage Δ
...s/opentelemetry-instrumentation-fetch/src/fetch.ts	96.00% <0.00%> (ø)
...mentation-xml-http-request/src/enums/EventNames.ts	100.00% <0.00%> (ø)
...-instrumentation-fetch/src/enums/AttributeNames.ts	100.00% <0.00%> (ø)
...emetry-instrumentation-xml-http-request/src/xhr.ts	96.79% <0.00%> (ø)
...emetry-core/src/platform/node/RandomIdGenerator.ts	93.75% <0.00%> (+6.25%)	⬆️