chore: replaced substr() with substring()

[k-rajat19]

I think we should try to avoid using deprecated functions, just added a small fix for that in this PR.

[codecov]

Codecov Report

Merging #2929 (aabe33c) into develop (90f4449) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2929   +/-   ##
========================================
  Coverage    90.96%   90.96%           
========================================
  Files           21       21           
  Lines         1151     1151           
  Branches       349      349           
========================================
  Hits          1047     1047           
  Misses         104      104           

Flag	Coverage Δ
cli	82.10% <ø> (ø)
integration	41.00% <ø> (ø)
library	58.55% <ø> (ø)
unit	75.06% <ø> (ø)

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

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 90f4449...aabe33c. Read the comment docs.