DOC: ignore Panel deprecation warnings during doc build

[jorisvandenbossche]

The doc build log is currently full of Panel deprecation warnings. To avoid having to put :okwarning: on all code-blocks that use Panel, I put a general filterwarnings for this warning in the conf.py file which hopefully works (alternative would be to put this inside the .rst file itself at the top in a suppressed ipython code block)

[codecov]

Codecov Report

Merging #19663 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #19663      +/-   ##
==========================================
- Coverage   91.58%   91.58%   -0.01%     
==========================================
  Files         150      150              
  Lines       48806    48864      +58     
==========================================
+ Hits        44701    44750      +49     
- Misses       4105     4114       +9

Flag	Coverage Δ
#multiple	89.95% <ø> (-0.01%)	⬇️
#single	41.75% <ø> (+0.02%)	⬆️

Impacted Files	Coverage Δ
pandas/io/s3.py	72.72% <0%> (-13.64%)	⬇️
pandas/io/packers.py	87.31% <0%> (-1.34%)	⬇️
pandas/core/arrays/base.py	60% <0%> (-0.61%)	⬇️
pandas/io/json/json.py	92.23% <0%> (-0.37%)	⬇️
pandas/io/common.py	68.77% <0%> (-0.3%)	⬇️
pandas/io/parquet.py	71.79% <0%> (-0.28%)	⬇️
pandas/io/parsers.py	95.32% <0%> (-0.25%)	⬇️
pandas/core/series.py	94.56% <0%> (-0.05%)	⬇️
pandas/core/frame.py	97.16% <0%> (-0.02%)	⬇️
pandas/core/indexes/multi.py	95.06% <0%> (-0.01%)	⬇️
... and 10 more

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[TomAugspurger]

Seems to have not gotten all of them: https://travis-ci.org/pandas-dev/pandas/jobs/340640054#L2633

[jorisvandenbossche]

Or rather, none of them ... :(
(I have to admit, I only tested the filterwarnings in an interactive session, not in combination with ipython directive)

[jorisvandenbossche]

New commits seems to work (and is simpler)