options: Remove parsing `--verbose` from the configuration file

The `--verbose` option is only used by `flake8`, itself,` when parsing
and handling preliminary options.  After parsing and merging options
from the configuration file, there is no other behavioral impact to the
core of `flake8`.  In other words, setting `verbose = ...` in a
configuration file doesn't change the logging verbosity.

While the `FileProcessor` does expose a `verbose` attribute, obtained
from the parsed options, the verbosity of the core of `flake8` should be
consistent with how a plugin may respond to the attribute's value.