Remove the Validate always section in validator docs (#6679)

docs/usage/validators.md

@@ -321,37 +321,6 @@ print(Model(a='invalid').a)
 #> 2000-01-01 00:00:00
 ```
 
-## Validate always
-
-**TODO this content is wrong!**
-
-For performance reasons, by default validators are not called for fields when a value is not supplied.
-However there are situations where it may be useful or required to always call the validator, e.g.
-to set a dynamic default value.
-
-```py
-from datetime import datetime
-
-from pydantic import BaseModel, field_validator
-
-
-class DemoModel(BaseModel):
-    ts: datetime
-
-    @field_validator('ts', mode='before')
-    def set_ts_now(cls, v):
-        return v or datetime.now()
-
-
-print(DemoModel(ts=None))
-#> ts=datetime.datetime(2032, 1, 2, 3, 4, 5, 6)
-print(DemoModel(ts='2017-11-08T14:00'))
-#> ts=datetime.datetime(2017, 11, 8, 14, 0)
-```
-
-You'll often want to use this together with `pre`, since otherwise with `always=True`
-Pydantic would try to validate the default `None` which would cause an error.
-
 ## Reuse validators
 
 Occasionally, you will want to use the same validator on multiple fields/models (e.g. to