Remove backport importlib_metadata from required dependencies

[agriyakhetarpal]

Description

A quick fix to replace the dependency on the backported module importlib_metadata with the standard module importlib.metadata, since we had dropped support for Python 3.7 and below in #2370

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ pre-commit run (see CONTRIBUTING.md for how to set this up to run automatically when committing locally, in just two lines of code)
• All tests pass: $ python run-tests.py --all
• The documentation builds: $ python run-tests.py --doctest

You can run unit and doctests together at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (abc53f5) 99.71% compared to head (9623c9b) 99.71%.

❗ Current head 9623c9b differs from pull request most recent head facd037. Consider uploading reports for the commit facd037 to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3050   +/-   ##
========================================
  Coverage    99.71%   99.71%           
========================================
  Files          248      248           
  Lines        18736    18736           
========================================
  Hits         18682    18682           
  Misses          54       54           

Impacted Files	Coverage Δ
pybamm/parameters/parameter_sets.py	100.00% <100.00%> (ø)

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