Remove obsolete typeguard checks

[epenet]

Follow-up to #263

[dairiki]

@lovasoa @epenet I am currently traveling and dealing with family medical issues.
I can probably find some time to look at this in the next couple of days, but nothing is certain.

I think this looks fine. The one thing that pops out on initial glance is that we might want to adjust our pins

marshmallow_dataclass/setup.py

Lines 49 to 55 in 4edbfb4

	install_requires=[
	"marshmallow>=3.18.0,",
	"typing-inspect~=0.9.0",
	"typeguard~=4.0.0",
	# Need `dataclass_transform(field_specifiers)`
	"typing-extensions>=4.2.0; python_version<'3.11'",
	],

I think we might want to adjust these to typeguard ~= 4.0 (to address #272) .
And maybe typing-inspect >= 0.9.0 (semver does not apply to 0.* versions).

[epenet]

I created a separate PR to fix #272
See #273