Fix issues with helm chart release process

[Sovietaced]

I am currently attempting to get our fork of Flyte to push helm charts to our artifact store and I ran into some issues. This pull request fixes two issues.

1. Updates the script to find/replace the version of the flyteagent helm chart such that flyte-core is able to find a matching version of the relative helm chart reference when doing helm dependency update. This should publish an actual updated version of the flyteagent helm chart instead of overwriting it (and potentially breaking peoples deployments) : https://artifacthub.io/packages/helm/flyte/flyteagent
2. Updates the script to patch each respective README instead of continuously overwriting the flyte-core README. This should fix the broken README that is currently live for flyte-core: https://artifacthub.io/packages/helm/flyte/flyte-core

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.97%. Comparing base (b7e6959) to head (6fbc922).
Report is 119 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5560      +/-   ##
==========================================
- Coverage   60.98%   60.97%   -0.01%     
==========================================
  Files         796      796              
  Lines       51647    51647              
==========================================
- Hits        31498    31494       -4     
- Misses      17249    17253       +4     
  Partials     2900     2900              

Flag	Coverage Δ
unittests-datacatalog	69.31% <ø> (ø)
unittests-flyteadmin	58.69% <ø> (-0.05%)	⬇️
unittests-flytecopilot	17.79% <ø> (ø)
unittests-flytectl	67.49% <ø> (+0.05%)	⬆️
unittests-flyteidl	79.06% <ø> (ø)
unittests-flyteplugins	61.85% <ø> (ø)
unittests-flytepropeller	57.42% <ø> (ø)
unittests-flytestdlib	65.65% <ø> (-0.03%)	⬇️

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