Update Starlette to >=0.21.0

[adriangb]

No description provided.

[adriangb]

Blocked by encode/starlette#1890

[codecov-commenter]

Codecov Report

Merging #108 (7ed3bcd) into main (ae15865) will decrease coverage by 0.23%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #108      +/-   ##
==========================================
- Coverage   98.34%   98.10%   -0.24%     
==========================================
  Files         123      123              
  Lines        4226     4224       -2     
  Branches      417      415       -2     
==========================================
- Hits         4156     4144      -12     
- Misses         35       40       +5     
- Partials       35       40       +5     

Impacted Files	Coverage Δ
...ests/test_docs/tutorial/forms/test_tutorial_003.py	100.00% <ø> (ø)
...st_docs/tutorial/dependencies/test_tutorial_007.py	100.00% <100.00%> (ø)
...ests/test_docs/tutorial/files/test_tutorial_004.py	100.00% <100.00%> (ø)
...ests/test_docs/tutorial/forms/test_tutorial_001.py	100.00% <100.00%> (ø)
...ests/test_docs/tutorial/forms/test_tutorial_002.py	100.00% <100.00%> (ø)
...st_docs/tutorial/query_params/test_tutorial_004.py	100.00% <100.00%> (ø)
tests/test_request_bodies/test_file.py	96.80% <100.00%> (-3.21%)	⬇️
tests/test_request_bodies/test_form.py	100.00% <100.00%> (ø)
tests/test_request_bodies/test_json.py	100.00% <100.00%> (ø)
tests/test_request_bodies/test_multipart.py	98.59% <100.00%> (-1.41%)	⬇️
... and 3 more