RFR: 8278071: typos in MemorySegment::set, MemorySegment::setAtIndex javadoc

[Maurizio Cimadamore]

There are some truncated statements in MemorySegment::get/MemorySegment::getAtIndex javadoc, more specifically in the `@throws` for `IndexOutOfBoundsException`.

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Commit messages:
 - Fix typos in MemorySegment dereference setters

Changes: https://git.openjdk.java.net/jdk/pull/6635/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6635&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278071
  Stats: 16 lines in 1 file changed: 16 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6635.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6635/head:pull/6635

PR: https://git.openjdk.java.net/jdk/pull/6635