DOCS: fix PR09,PR09 doc string errors in Timestamp, NaT, Timedelta class
This fixes validation errors PR09,PR08 for pandas.Timestamp, pandas.Timedelta (and also NaT) class:

```
pandas.Timestamp.ceil: Parameter "ambiguous" description should start with a capital letter
pandas.Timestamp.ceil: Parameter "ambiguous" description should finish with "."
pandas.Timestamp.ceil: Parameter "nonexistent" description should finish with "."
pandas.Timestamp.day_name: Parameter "locale" description should start with a capital letter
pandas.Timestamp.day_name: Parameter "locale" description should finish with "."
pandas.Timestamp.floor: Parameter "ambiguous" description should start with a capital letter
pandas.Timestamp.floor: Parameter "ambiguous" description should finish with "."
pandas.Timestamp.floor: Parameter "nonexistent" description should finish with "."
pandas.Timestamp.fromordinal: Parameter "ordinal" description should start with a capital letter
pandas.Timestamp.fromordinal: Parameter "ordinal" description should finish with "."
pandas.Timestamp.fromordinal: Parameter "freq" description should finish with "."
pandas.Timestamp.month_name: Parameter "locale" description should start with a capital letter
pandas.Timestamp.month_name: Parameter "locale" description should finish with "."
pandas.Timestamp.now: Parameter "tz" description should finish with "."
pandas.Timestamp.round: Parameter "ambiguous" description should start with a capital letter
pandas.Timestamp.round: Parameter "ambiguous" description should finish with "."
pandas.Timestamp.round: Parameter "nonexistent" description should finish with "."
pandas.Timestamp.today: Parameter "tz" description should finish with "."
pandas.Timestamp.tz_localize: Parameter "ambiguous" description should finish with "."
pandas.Timestamp.tz_localize: Parameter "nonexistent" description should finish with "."
pandas.Timestamp.tz_localize: Parameter "errors" description should start with a capital letter
pandas.Timestamp.tz_localize: Parameter "errors" description should finish with "."
pandas.Timedelta.max: Parameter "unit" description should finish with "."
pandas.Timedelta.min: Parameter "unit" description should finish with "."
```

This is a subset of #28602 and #27977 
