Bump StableHLO to openxla/stablehlo@23d7f60. (#19754)

This includes LLVM updates in StableHLO that resolve compiler warnings
like
```
[5467/8397] Building CXX object llvm-external-projects/stablehlo/stablehlo/transforms/CMakeFiles/obj.StablehloPasses.dir/StablehloCanonicalizeDynamism.cpp.o
/__w/iree/iree/third_party/stablehlo/stablehlo/transforms/StablehloCanonicalizeDynamism.cpp:326:16: warning: 'applyPatternsAndFoldGreedily' is deprecated: Use applyPatternsGreedily() instead [-Wdeprecated-declarations]
    if (failed(applyPatternsAndFoldGreedily(func, patterns, config))) {
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
               applyPatternsGreedily
/__w/iree/iree/third_party/llvm-project/mlir/include/mlir/Transforms/GreedyPatternRewriteDriver.h:184:1: note: 'applyPatternsAndFoldGreedily' has been explicitly marked deprecated here
LLVM_DEPRECATED("Use applyPatternsGreedily() instead", "applyPatternsGreedily")
^
/__w/iree/iree/third_party/llvm-project/llvm/include/llvm/Support/Compiler.h:234:50: note: expanded from macro 'LLVM_DEPRECATED'
#define LLVM_DEPRECATED(MSG, FIX) __attribute__((deprecated(MSG, FIX)))
                                                 ^
1 warning generated.
```

(thanks to
openxla/stablehlo@b2d36c5)