Stop importing deprecated pkg_resources module

[ni-jfitzger]

• This contribution adheres to CONTRIBUTING.md.
• [ ] I've updated CHANGELOG.md if applicable.
• [ ] I've added tests applicable for this pull request

What does this Pull Request accomplish?

Delete the dead code that allows conditional importing of pkg_resources.
I should have done this when dropping Python 3.9 support.

List issues fixed by this Pull Request below, if any.

• Fix Drop Python 3.9 support when it goes EOL #2047

What testing has been done?

PR Checks

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.09%. Comparing base (fb4aee8) to head (c61492e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2160      +/-   ##
==========================================
+ Coverage   90.07%   90.09%   +0.01%     
==========================================
  Files          71       71              
  Lines       18666    18662       -4     
==========================================
  Hits        16814    16814              
+ Misses       1852     1848       -4     

Flag	Coverage Δ
codegenunittests	84.44% <ø> (ø)
nidcpowersystemtests	94.65% <ø> (+0.04%)	⬆️
nidcpowerunittests	89.53% <ø> (ø)
nidigitalsystemtests	92.26% <ø> (ø)
nidigitalunittests	68.44% <ø> (ø)
nidmmsystemtests	92.72% <ø> (ø)
nifakeunittests	85.70% <100.00%> (+0.19%)	⬆️
nifgensystemtests	94.61% <ø> (ø)
nimodinstsystemtests	73.85% <ø> (ø)
nimodinstunittests	94.20% <ø> (ø)
nirfsgsystemtests	82.40% <ø> (ø)
niscopesystemtests	92.94% <ø> (ø)
niscopeunittests	43.20% <ø> (ø)
nisesystemtests	91.50% <ø> (ø)
niswitchsystemtests	82.03% <ø> (ø)
nitclksystemtests	94.87% <ø> (ø)
nitclkunittests	98.26% <ø> (ø)

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Files with missing lines	Coverage Δ
generated/nifake/nifake/__init__.py	84.72% <100.00%> (+3.14%)	⬆️

... and 1 file with indirect coverage changes

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