chore(aws): replace deprecated substr with substring

[trivikr]

Which problem is this PR solving?

• The String.prototype.substr() is deprecated.

Short description of the changes

• This PR replaces String.prototype.substr() with String.prototype.substring()

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.75%. Comparing base (d5215f3) to head (6fbb3b1).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2551      +/-   ##
==========================================
- Coverage   90.80%   90.75%   -0.05%     
==========================================
  Files         169      169              
  Lines        8018     8018              
  Branches     1632     1632              
==========================================
- Hits         7281     7277       -4     
- Misses        737      741       +4     

Files with missing lines	Coverage Δ
...-instrumentation-aws-lambda/src/instrumentation.ts	93.60% <100.00%> (ø)
...emetry-instrumentation-aws-sdk/src/services/sns.ts	94.11% <100.00%> (ø)

... and 1 file with indirect coverage changes

[pichlermarc]

Thanks 🙌