RFR: 8255904: Remove superfluous use of reflection in Class::isRecord

[Chris Hegarty]

Minor cleanup - Reflective access to j.l.Record is no longer required since it became standard.

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Commit messages:
 - 8255904: Remove superfluous use of reflection in Class::isRecord

Changes: https://git.openjdk.java.net/jdk/pull/1406/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1406&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255904
  Stats: 11 lines in 1 file changed: 0 ins; 10 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1406.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1406/head:pull/1406

PR: https://git.openjdk.java.net/jdk/pull/1406