[Mlir-commits] [mlir] [mlir] Remove unused DenseMapInfo::getEmptyKey (PR #201991)

[Fangrui Song]

MaskRay wrote:

```
git diff -U0  --relative 'HEAD^'...  | ~/llvm/clang/tools/clang-format/clang-format-diff.py -p1 -i
```
with latest clang-format doesn't complain. I'm going to ignore the code_formatter checker.

https://github.com/llvm/llvm-project/pull/201991