NFC: fix comment in WasmImpl.swift (#80760)

Wasm is not an acronym, thus it's not uppercased [per the spec](https://webassembly.github.io/spec/core/intro/introduction.html#wasm).

Author: MaxDesiatov

stdlib/public/Synchronization/Mutex/WasmImpl.swift

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// Note: All atomic accesses on WASM are sequentially consistent regardless of
+// Note: All atomic accesses on Wasm are sequentially consistent regardless of
 // what ordering we tell LLVM to use.
 
 @_extern(c, "llvm.wasm.memory.atomic.wait32")