Remove text file object support

[hukkin]

TODO:

• add changelog entry (v2.0.0)

[codecov-commenter]

Codecov Report

Merging #133 (ac49062) into master (96dfe2c) will not change coverage.
The diff coverage is 100.00%.

❗ Current head ac49062 differs from pull request most recent head 5837989. Consider uploading reports for the commit 5837989 to get more accurate results

@@            Coverage Diff            @@
##            master      #133   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          495       489    -6     
  Branches        93        93           
=========================================
- Hits           495       489    -6     

Impacted Files	Coverage Δ
tomli/_parser.py	100.00% <100.00%> (ø)
tomli/__init__.py	100.00% <0.00%> (ø)

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