<Swing Dev> RFR: 8253792: javax.swing.text.GapContent documentation typos

[Prasanta Sadhukhan]

Fixed some documentation typos

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Commit messages:
 - 8253792: javax.swing.text.GapContent documentation typos

Changes: https://git.openjdk.java.net/jdk/pull/421/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=421&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253792
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/421.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/421/head:pull/421

PR: https://git.openjdk.java.net/jdk/pull/421