RFR: 8352948: Remove leftover runtime_x86_32.cpp after 32-bit x86 removal

[Aleksey Shipilev]

As I merged [JDK-8345169](https://bugs.openjdk.org/browse/JDK-8345169), I noticed one more file was left over:


$ find | grep x86_32
./src/hotspot/cpu/x86/runtime_x86_32.cpp


My bad, this PR removes that leftover.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/24249/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24249&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352948
  Stats: 332 lines in 1 file changed: 0 ins; 332 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24249/head:pull/24249

PR: https://git.openjdk.org/jdk/pull/24249