Remove unused arguments from np_datetime_strings

[jbrockmendel]

Same deal as #18546. This completes the pure-cleaning phase for np_datetime_strings.

[codecov]

Codecov Report

Merging #18565 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #18565      +/-   ##
==========================================
- Coverage   91.35%   91.33%   -0.02%     
==========================================
  Files         164      164              
  Lines       49802    49802              
==========================================
- Hits        45496    45487       -9     
- Misses       4306     4315       +9

Flag	Coverage Δ
#multiple	89.13% <ø> (ø)	⬆️
#single	40.81% <ø> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.81% <0%> (-0.1%)	⬇️

---

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[codecov]

Codecov Report

Merging #18565 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #18565      +/-   ##
==========================================
- Coverage   91.59%   91.58%   -0.02%     
==========================================
  Files         155      153       -2     
  Lines       51255    51253       -2     
==========================================
- Hits        46948    46941       -7     
- Misses       4307     4312       +5

Flag	Coverage Δ
#multiple	89.45% <ø> (ø)	⬆️
#single	40.67% <ø> (-0.11%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.81% <0%> (-0.1%)	⬇️
pandas/io/data.py
pandas/io/wb.py
pandas/util/testing.py	82.01% <0%> (+0.19%)	⬆️

---

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[jbrockmendel]

After this and #18567 there are two more PRs on deck to simplify src/datetime.

[jreback]

yep rebase

[jbrockmendel]

Travis error is a timeout, looks unrelated. Will re-push this evening.

[jreback]

lgtm. ping on green.

[jbrockmendel]

ping

[jbrockmendel]

Once this is closed we can kill off datetime.pxd

[jreback]

kill it!