RFR: 8256009: Remove src/hotspot/share/adlc/Test/i486.ad

[Jie Fu]

src/hotspot/share/adlc/Test/i486.ad is empty.
It might be better to remove it.
Thanks.

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Commit messages:
 - 8256009: Remove src/hotspot/share/adlc/Test/i486.ad

Changes: https://git.openjdk.java.net/jdk/pull/1107/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1107&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256009
  Stats: 0 lines in 1 file changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1107.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1107/head:pull/1107

PR: https://git.openjdk.java.net/jdk/pull/1107