[Backport 2.x] Fix `sed` invocation in version bump workflow

[opensearch-trigger-bot[bot]]

Backport 58dd55bb88af5fd511e00f72f30a2a4a5c632e3e from #206

[codecov[bot]]

Codecov Report

Merging #207 (f6ab759) into 2.x (2d13584) will not change coverage. Report is 1 commits behind head on 2.x. The diff coverage is n/a.

@@           Coverage Diff           @@
##              2.x     #207   +/-   ##
=======================================
  Coverage   73.83%   73.83%           
=======================================
  Files         403      403           
  Lines       63777    63777           
=======================================
  Hits        47092    47092           
  Misses      16685    16685           

Flag	Coverage Δ
integration	73.83% <ø> (ø)

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