[ARM][WebAssembly] Remove unused PatternMatch namespace. NFC.

Avoid file-level "using namespace llvm::PatternMatch" to make it easier to potentially use SDPatternMatch in the future.

Author: RKSimon

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -115,7 +115,6 @@
 #include <vector>
 
 using namespace llvm;
-using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "arm-isel"
 

llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp

@@ -35,10 +35,8 @@
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Operator.h"
-#include "llvm/IR/PatternMatch.h"
 
 using namespace llvm;
-using namespace PatternMatch;
 
 #define DEBUG_TYPE "wasm-fastisel"