Remove Panel References from Tests

[WillAyd]

ref #25632 this removes a good deal of Panel references from tests though not all (excluding anything for msgpack).

I think after this and #25567 get merged we can starting finalizing the Panel removal and get out of docs as well

[WillAyd]

This was a little bit more movement on the test than I had hoped for but the original test mentions something of this reshaping to be "a little bit crude" so it may be in order; new test should have the same coverage but with less reshaping

[codecov]

Codecov Report

Merging #26332 into master will decrease coverage by 0.24%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #26332      +/-   ##
==========================================
- Coverage   92.04%    91.8%   -0.25%     
==========================================
  Files         175      175              
  Lines       52297    52297              
==========================================
- Hits        48137    48011     -126     
- Misses       4160     4286     +126

Flag	Coverage Δ
#multiple	90.35% <ø> (-0.24%)	⬇️
#single	40.72% <ø> (-0.15%)	⬇️

Impacted Files	Coverage Δ
pandas/core/panel.py	17.49% <0%> (-17.65%)	⬇️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/generic.py	93.34% <0%> (-0.24%)	⬇️
pandas/core/frame.py	97.01% <0%> (-0.12%)	⬇️

---

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[codecov]

Codecov Report

Merging #26332 into master will decrease coverage by 0.24%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #26332      +/-   ##
==========================================
- Coverage   92.04%    91.8%   -0.25%     
==========================================
  Files         175      175              
  Lines       52297    52297              
==========================================
- Hits        48137    48011     -126     
- Misses       4160     4286     +126

Flag	Coverage Δ
#multiple	90.35% <ø> (-0.24%)	⬇️
#single	40.72% <ø> (-0.15%)	⬇️

Impacted Files	Coverage Δ
pandas/core/panel.py	17.49% <0%> (-17.65%)	⬇️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/generic.py	93.34% <0%> (-0.24%)	⬇️
pandas/core/frame.py	97.01% <0%> (-0.12%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ee6b131...729edea. Read the comment docs.

[jreback]

looks ok, pending CI build issues.

[jreback]

thanks @WillAyd