Fix mistakes in codecov.yml

[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?

The codecov.yml was invalid due to a misspelled key.
The codecov app pointed this out.

See https://docs.codecov.com/docs/commit-status#threshold

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

None

What testing has been done?

Validated the .yml with codecov's validator.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.51%. Comparing base (d9b2a31) to head (a4fc99b).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2203   +/-   ##
=======================================
  Coverage   88.51%   88.51%           
=======================================
  Files          82       82           
  Lines       21679    21679           
=======================================
+ Hits        19189    19190    +1     
+ Misses       2490     2489    -1     

Flag	Coverage Δ
codegenunittests	84.90% <ø> (ø)
nidcpowersystemtests	94.38% <ø> (+0.04%)	⬆️
nidcpowerunittests	89.53% <ø> (ø)
nidigitalsystemtests	92.02% <ø> (ø)
nidigitalunittests	68.44% <ø> (ø)
nidmmsystemtests	92.29% <ø> (ø)
nifakeunittests	86.01% <ø> (ø)
nifgensystemtests	94.32% <ø> (ø)
nimodinstsystemtests	73.85% <ø> (ø)
nimodinstunittests	94.20% <ø> (ø)
nirfsasystemtests	82.66% <ø> (ø)
nirfsgsystemtests	81.12% <ø> (ø)
niscopesystemtests	89.96% <ø> (ø)
niscopeunittests	43.20% <ø> (ø)
nisesystemtests	91.50% <ø> (ø)
niswitchsystemtests	81.56% <ø> (ø)
nitclksystemtests	94.87% <ø> (ø)
nitclkunittests	98.26% <ø> (ø)

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