RFR: 8294255: Add link to DEFAULT_WAIT_TIME in javadoc for SunToolKit.realsSync

[SWinxy]

I also took the opportunity to link to `realSync(long)`.

/**
  * Parameterless version of realsync which uses default timout (see DEFAUL_WAIT_TIME).
  */


/**
  * Parameterless version of {@link #realSync(long)} which uses
  * the default timeout of {@link #DEFAULT_WAIT_TIME}.
  */

-------------

Commit messages:
 - 8294255: Add link to DEFAULT_WAIT_TIME in javadoc for SunToolKit.realsSync

Changes: https://git.openjdk.org/jdk/pull/10399/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10399&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294255
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10399.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10399/head:pull/10399

PR: https://git.openjdk.org/jdk/pull/10399