RFR: 8252807: The jdk.jfr.Recording.getStream does not work when toDisk is disabled

[Erik Gahlin]

Clarify that an InputStream can't be return when calling Recording::getStream() on an in memory recording.

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Commit messages:
 - Remove trailing space
 - Initial

Changes: https://git.openjdk.java.net/jdk/pull/1592/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1592&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252807
  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1592.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1592/head:pull/1592

PR: https://git.openjdk.java.net/jdk/pull/1592