RFR: 8290964: C2 compilation fails with assert "non-reduction loop contains reduction nodes"

[Roberto Castañeda Lozano]

This changeset removes the [reduction information consistency assertion](https://github.com/openjdk/jdk/blob/46633e644a8ab94ceb75803bd40739214f8a60e8/src/hotspot/share/opto/superword.cpp#L2458-L2459) in `SuperWord::output()`, which has proven to report too many false positives (inconsistencies that do not lead to miscompilation) since its introduction by [JDK-8279622](https://bugs.openjdk.org/browse/JDK-8279622), despite the efforts to reduce the false positive rate in [JDK-8286177](https://bugs.openjdk.org/browse/JDK-8286177). During the time the assertion has been enabled in our internal CI system, no true positive case (reported inconsistencies actually leading to a miscompilation or a crash) has been observed.

An alternative solution would be to wait for [JDK-8287087](https://bugs.openjdk.org/browse/JDK-8287087) (work in progress), which proposes a refactoring of the reduction analysis logic that eliminates by construction the need for this assertion. This changeset proposes removing the assertion earlier, to reduce noise in test environments.

#### Testing

- hs-tier1 (windows-x64, linux-x64, linux-aarch64, and macosx-x64).

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Commit messages:
 - Remove noisy assertion

Changes: https://git.openjdk.org/jdk/pull/10535/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10535&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290964
  Stats: 21 lines in 3 files changed: 0 ins; 21 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10535.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10535/head:pull/10535

PR: https://git.openjdk.org/jdk/pull/10535