[WebAssembly] Add `final` keywords to a few more subclasses, for consistency.

llvm-svn: 263287
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyPEI.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyPEI.cpp
index d00ae70..ca55fef5 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyPEI.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyPEI.cpp
@@ -59,7 +59,7 @@
 void initializeWasmPEIPass(PassRegistry&);
 }
 namespace {
-class WasmPEI : public MachineFunctionPass {
+class WasmPEI final : public MachineFunctionPass {
 public:
   static char ID;
   WasmPEI() : MachineFunctionPass(ID) {