Fix using tuples as positional arguments in rich repr

[saulshanabrook]

Type of changes

• Bug fix
• New feature
• Documentation / docstrings
• Tests
• Other

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• I've added tests for new code.
• I accept that @willmcgugan may be pedantic in the code review.

Description

Currently, it isn't possible to use tuples as positional arguments from __rich_repr__, because they are special cased to support adding a key and a default value.

This adds support for them, by allowing None as a key.

[willmcgugan]

This already works:

class Foo:
    def __rich_repr__(self):
        yield None, (1,)

f=Foo()
from rich import print
print(f)

If its not documented, that should certainly be rectified.

[codecov-commenter]

Codecov Report

Merging #2379 (21b51aa) into master (19e518f) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2379      +/-   ##
==========================================
- Coverage   98.71%   98.67%   -0.05%     
==========================================
  Files          73       72       -1     
  Lines        7771     7746      -25     
==========================================
- Hits         7671     7643      -28     
- Misses        100      103       +3     

Flag	Coverage Δ
unittests	98.67% <100.00%> (-0.05%)	⬇️

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Impacted Files	Coverage Δ
rich/default_styles.py	100.00% <ø> (ø)
rich/_inspect.py	100.00% <100.00%> (ø)
rich/cells.py	96.05% <100.00%> (-3.95%)	⬇️
rich/console.py	98.30% <100.00%> (+0.01%)	⬆️
rich/pretty.py	99.21% <100.00%> (-0.01%)	⬇️
rich/style.py	99.75% <100.00%> (-0.01%)	⬇️
rich/syntax.py	99.37% <100.00%> (+0.07%)	⬆️

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[saulshanabrook]

@willmcgugan Oh whoops! I guess I should have tested it first :)

I updated this PR to remove the code changes, but keep the tests and docs.