docs: Fix a few typos

[timgates42]

There are small typos in:

• docs/runner.rst
• docs/usage.rst
• src/waitress/parser.py
• src/waitress/server.py
• tests/test_functional.py

Fixes:

• Should read preceding rather than preceeding.
• Should read multiple rather than multipe.
• Should read descriptors rather than desctriptors.
• Should read descriptor rather than desctriptor.
• Should read attempt rather than atempt.
• Should read analogous rather than analagous.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md