fix(chips): md-chip-append-delay of 0 does not get converted to 300

[Splaktar]

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PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Using 0 for md-chip-append-delay causes the directive to convert 0 to 300ms due to a bad if check. This is a regression caused by the chips a11y updates in 1.1.2.

Issue Number:
Fixes #10408

What is the new behavior?

Setting md-chip-append-delay to 0 now removes the delay completely as expected.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

Thanks to @mgol for the report and corrected code snippet.