Internals: Fix missing newline on co_return output code

src/V3EmitCFunc.h

@@ -478,7 +478,7 @@ public:
         if (nodep->isCoroutine()) {
             // Sometimes coroutines don't have co_awaits,
             // so emit a co_return at the end to avoid compile errors.
-            puts("co_return;");
+            puts("co_return;\n");
         }
 
         puts("}\n");