Simplify (and optimize) Descriptors.FileDescriptor.latin1Cat.

PiperOrigin-RevId: 603529248

java/core/src/main/java/com/google/protobuf/Descriptors.java

@@ -415,11 +415,7 @@ public final class Descriptors {
       if (strings.length == 1) {
         return strings[0].getBytes(Internal.ISO_8859_1);
       }
-      StringBuilder descriptorData = new StringBuilder();
+      return String.join("", strings).getBytes(Internal.ISO_8859_1);
-      for (String part : strings) {
-        descriptorData.append(part);
-      }
-      return descriptorData.toString().getBytes(Internal.ISO_8859_1);
     }
 
     private static FileDescriptor[] findDescriptors(