Fix StrictStr does not raise ValidationError when max_length is present in Field

[hramezani]

ref #4383.

Change Summary

same as the fix for StrictBytes.

Without this patch, the following code fails:

from pydantic import BaseModel, Field, StrictStr

class Model(BaseModel):
    a: StrictStr = Field(...)
    b: StrictStr = Field(..., max_length=5)

print(Model(a="123", b="123"))

Traceback (most recent call last):
  File "/tmp/test.py", line 3, in <module>
    class Model(BaseModel):
  File "/home/hasan/work/pydantic/pydantic/main.py", line 198, in __new__
    fields[ann_name] = ModelField.infer(
  File "/home/hasan/work/pydantic/pydantic/fields.py", line 497, in infer
    annotation = get_annotation_from_field_info(annotation, field_info, name, config.validate_assignment)
  File "/home/hasan/work/pydantic/pydantic/schema.py", line 1011, in get_annotation_from_field_info
    raise ValueError(
ValueError: On field "b" the following field constraints are set but not enforced: max_length. 
For more details see https://pydantic-docs.helpmanual.io/usage/schema/#unenforced-field-constraints

Related issue number

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• changes/<pull request or issue id>-<github username>.md file added describing change
  (see changes/README.md for details)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[hramezani]

please review

[samuelcolvin]

great, thanks so much.