[LoopInterchange] Update tests for reduction2mem (NFC) (#181629)
The current ongoing work on DependenceAnalysis will degrade its analysis
capability. As a result, some existing tests will start to fail, meaning
that those tests are no longer meaningful. To preserve their original
intent, they need to be updated so that DependenceAnalysis can still
analyze them accurately.
This patch updates the test cases for the reduction2mem feature in
LoopInterchange. Specifically, it replaces the loop bounds with constant
values, which should not alter the intent of the tests.