Remove unused repo methods

[Sovietaced]

Why are the changes needed?

Simplify the codebase.

What changes were proposed in this pull request?

Removed task execution and node execution count methods. I discovered these while implementing support for read replicas in our fork.

Labels

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• added: For new features.
• changed: For changes in existing functionality.
• deprecated: For soon-to-be-removed features.
• removed: For features being removed.
• fixed: For any bug fixed.
• security: In case of vulnerabilities

This is important to improve the readability of release notes.

Setup process

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• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.43%. Comparing base (2e10675) to head (83533b6).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7637      +/-   ##
==========================================
- Coverage   57.20%   56.43%   -0.77%     
==========================================
  Files         930      771     -159     
  Lines       58253    52194    -6059     
==========================================
- Hits        33322    29457    -3865     
+ Misses      21870    19978    -1892     
+ Partials     3061     2759     -302     

Flag	Coverage Δ
unittests-datacatalog	53.51% <ø> (ø)
unittests-flyteadmin	53.25% <ø> (+0.07%)	⬆️
unittests-flytecopilot	48.05% <ø> (ø)
unittests-flytectl	?
unittests-flyteidl	75.71% <ø> (ø)
unittests-flyteplugins	60.38% <ø> (ø)
unittests-flytepropeller	53.78% <ø> (ø)
unittests-flytestdlib	64.41% <ø> (ø)

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