fix: allow google-cloud-documentai < 3

[parthea]

The templated setup.py has a constraint on google-cloud-documentai < 2. We should allow google-cloud-documentai < 3. See google-cloud-documentai releases here.

gapic-generator-python/gapic/templates/setup.py.j2

Lines 37 to 39 in 70d7882

	{% if api.requires_package(('google', 'cloud', 'documentai', 'v1')) %}
	'google-cloud-documentai >= 1.2.1, < 2.0.0dev',
	{% endif %}