fix(material/core): correct createDate JSDoc return description

[BHUVANSH855]

PR Checklist

• The commit message follows our guidelines
• Tests for the changes have been added (not needed for docs-only change)
• Docs have been added / updated

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Documentation Update

What is the current behavior?

The JSDoc for DateAdapter#createDate states that the method may return null when invalid:

@returnsThenewdate,ornullifinvalid.

However, the method signature returns D, not D | null, and implementations throw errors instead of returning null.

Closes#33059

What is the new behavior?

Updates the JSDoc return description to correctly reflect the actual behavior of the method.

[BHUVANSH855]

Hi @andrewseguin@wagnermaciel,

Just checking regarding this PR.
Any feedback.