Retrieve block signatures directly from block headers.

The placeholder block has replaced its signature now and retrieving its signature can be done in the same way as the regular blocks.

PiperOrigin-RevId: 343912714

Service/Sources/NSBlock+EDOInvocation.m

@@ -50,12 +50,7 @@ @implementation NSBlock (EDOInvocation)
   }
 
   IMP methodSignatureImp = imp_implementationWithBlock(^(id block, SEL selector) {
-    EDOBlockObject *blockObject = [EDOBlockObject EDOBlockObjectFromBlock:block];
-    if (blockObject) {
-      return [NSMethodSignature signatureWithObjCTypes:blockObject.signature.UTF8String];
-    } else {
-      return [NSMethodSignature signatureWithObjCTypes:[EDOBlockObject signatureFromBlock:block]];
-    }
+    return [NSMethodSignature signatureWithObjCTypes:[EDOBlockObject signatureFromBlock:block]];
   });
   BOOL methodSignatureAdded = class_addMethod(
       [NSBlock class], @selector(methodSignatureForSelector:), methodSignatureImp, "v@::");