[mlir] BUILD.bazel: remove LLVMDialect from MathTransforms

c1ebefd "[mlir] Make polynomial approximation emit
std instead of LLVM ops" removed the dependence on LLVMDialect.

Remove the dependence also from BUILD.bazel.

Reviewed By: bkramer

Differential Revision: https://reviews.llvm.org/D107908

Author: cota

utils/bazel/llvm-project-overlay/mlir/BUILD.bazel

@@ -6686,7 +6686,6 @@ cc_library(
     includes = ["include"],
     deps = [
         ":IR",
-        ":LLVMDialect",
         ":MathDialect",
         ":Pass",
         ":SCFDialect",