Template updates

[sgugger]

When adding the Funnel Transformer, I noticed a few things wrong in the template. This PR fixes those.

• using transformers.testing_utils instead of .utils
• remove xxx from names in tests (as @patrickvonplaten has done recently on Bert)
• add multiple choice model test
• fix label names in masked lm model
• remove the mention to add to pipelines.py in the checklist since there is nothing to do there

[codecov]

Codecov Report

Merging #6914 into master will increase coverage by 1.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6914      +/-   ##
==========================================
+ Coverage   77.81%   79.03%   +1.21%     
==========================================
  Files         157      157              
  Lines       28853    28853              
==========================================
+ Hits        22452    22804     +352     
+ Misses       6401     6049     -352     

Impacted Files	Coverage Δ
src/transformers/modeling_tf_mobilebert.py	24.55% <0.00%> (-72.36%)	⬇️
src/transformers/tokenization_pegasus.py	30.15% <0.00%> (-65.08%)	⬇️
src/transformers/modeling_roberta.py	77.73% <0.00%> (-19.35%)	⬇️
src/transformers/data/data_collator.py	92.30% <0.00%> (-0.41%)	⬇️
src/transformers/modeling_utils.py	88.05% <0.00%> (+0.18%)	⬆️
src/transformers/tokenization_utils.py	89.84% <0.00%> (+0.39%)	⬆️
src/transformers/generation_utils.py	97.21% <0.00%> (+0.83%)	⬆️
src/transformers/configuration_utils.py	96.64% <0.00%> (+1.34%)	⬆️
src/transformers/modeling_distilbert.py	97.84% <0.00%> (+1.61%)	⬆️
src/transformers/modelcard.py	85.18% <0.00%> (+2.46%)	⬆️
... and 12 more

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[LysandreJik]

LGTM, thanks @sgugger