chore(instrumentation-fetch): fix lint warnings

[alisabzevari]

related to #1093

Which problem is this PR solving?

• This PR fixes lint warnings in instrumentation-fetch package.

Short description of the changes

• Fix lint warnings.

[codecov]

Codecov Report

Merging #2454 (2d3727b) into main (6617573) will decrease coverage by 0.14%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##             main    #2454      +/-   ##
==========================================
- Coverage   92.73%   92.58%   -0.15%     
==========================================
  Files         137      134       -3     
  Lines        4996     4871     -125     
  Branches     1057     1036      -21     
==========================================
- Hits         4633     4510     -123     
+ Misses        363      361       -2     

Impacted Files	Coverage Δ
...s/opentelemetry-instrumentation-fetch/src/fetch.ts	96.96% <66.66%> (ø)
...sync-hooks/src/AbstractAsyncHooksContextManager.ts
...async-hooks/src/AsyncLocalStorageContextManager.ts
...ontext-async-hooks/src/AsyncHooksContextManager.ts

[obecny]

lgtm