Flake8-annotations

Fixed
* 100 Fix incorrect positioning of posonlyargs in the `Function` argument list, causing incorrect classification of the type of missing argument.

Fixed
* 92 Fix inconsistent linting behavior between function-level type comments and their equivalent PEP 3107-style function annotations of class methods and classmethods.
* 94 Fix improper handling of the closing definition in a series of `typing.overload` decorated functions.

Added
* 87 Add `--mypy-init-return` to allow omission of a return type hint for `__init__` if at least one argument is annotated. See [mypy's documentation](https://mypy.readthedocs.io/en/stable/class_basics.html?#annotating-init-methods) for additional details.

Fixed
* 89 Revert change to Python version pinning to prevent unnecessary locking headaches

Added
* 87 Add `--allow-untyped-defs` to suppress all errors from dynamically typed functions. A function is considered dynamically typed if it does not contain any type hints.

Fixed
* 77, 81 Fix incorrect return error locations in the presence of a multiline docstring containing colon(s)
* 81 Fix incorrect return error locations for single-line function definitions
* Fix incorrectly pinned project specifications

Added
* 68 Add `--suppress-dummy-args` configuration option to suppress ANN000 level errors for dummy arguments, defined as `"_"`