RFR: JDK-8299399: Remove metaprogramming/isArray.hpp

[Justin King]

Code cleanup of pre-C++11 <type_traits> implementations.

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

Commit messages:
 - Remove metaprogramming/isArray.hpp

Changes: https://git.openjdk.org/jdk/pull/11797/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11797&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299399
  Stats: 39 lines in 2 files changed: 2 ins; 36 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/11797.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11797/head:pull/11797

PR: https://git.openjdk.org/jdk/pull/11797