MFA format fix

[iamanigeeit]

The key changes in this fix are to treat apostrophes as word characters, and remove braces from transcripts. Both were causing mfa_format.py to fail on the LibriTTS corpus.

Other changes are for readability.

[codecov]

Codecov Report

Merging #5275 (93b136a) into master (c9cd4de) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5275   +/-   ##
=======================================
  Coverage   76.11%   76.11%           
=======================================
  Files         672      672           
  Lines       59864    59864           
=======================================
  Hits        45567    45567           
  Misses      14297    14297           

Flag	Coverage Δ
test_configuration_espnet2	∅ <ø> (∅)
test_integration_espnet1	65.93% <ø> (ø)
test_integration_espnet2	47.92% <ø> (ø)
test_python_espnet1	20.50% <ø> (ø)
test_python_espnet2	51.35% <ø> (ø)
test_utils	23.17% <ø> (ø)

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