Fix _shift_right function in TFT5PreTrainedModel

[maurice-g]

See ticket #5991

[codecov]

Codecov Report

Merging #6214 into master will decrease coverage by 0.17%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6214      +/-   ##
==========================================
- Coverage   79.66%   79.48%   -0.18%     
==========================================
  Files         146      146              
  Lines       26582    26584       +2     
==========================================
- Hits        21176    21131      -45     
- Misses       5406     5453      +47     

Impacted Files	Coverage Δ
src/transformers/modeling_tf_t5.py	90.95% <100.00%> (+0.03%)	⬆️
src/transformers/tokenization_marian.py	68.14% <0.00%> (-25.67%)	⬇️
src/transformers/tokenization_xlm_roberta.py	84.52% <0.00%> (-10.72%)	⬇️
src/transformers/tokenization_transfo_xl.py	33.56% <0.00%> (-8.93%)	⬇️
src/transformers/file_utils.py	80.05% <0.00%> (-0.26%)	⬇️
src/transformers/generation_tf_utils.py	86.46% <0.00%> (+1.25%)	⬆️
src/transformers/tokenization_bart.py	95.77% <0.00%> (+35.21%)	⬆️

---

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 9996f69...30e2c28. Read the comment docs.