refactor(input): deprecate accept property

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue URL: resolves #25500

The type property has never accepted 'file' as a valid value. However, our documentation makes references to 'file' in the multiple and accept properties.

Both descriptions were likely adapted from descriptions on MDN, which made reference to 'file'.

Additionally, the accept property was added to have greater parity with the native input: fe99d19 However, this was a mistake as ion-input never supported 'file'.

What is the new behavior?

• Deprecated the accept property
• Revised the accept property to state that it is ignored. It technically works if you force type to 'file', but 'file' is not a valid value. We could stop passing accept into the native input, but that would be a breaking change.
• Removed the 'file' reference from the multiple prop description.

Does this introduce a breaking change?

• Yes
• No

Other information