RFR: 8303232: java.util.Date.parse(String) and java.util.Date(String) don't declare thrown IllegalArgumentException

[Justin Lu]

The method `java.util.Date.parse(String)` and as a result, constructor `java.util.Date(String)` throw an `IllegalArgumentException`. This exception is not properly referenced in the javadoc, and this PR simply adds the throws javadoc tag to make it apparent.

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Commit messages:
 - Add @throws for Date(String), Date.parse(String)

Changes: https://git.openjdk.org/jdk/pull/12779/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12779&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303232
  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12779.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12779/head:pull/12779

PR: https://git.openjdk.org/jdk/pull/12779