[ObjC] Fix up clang-format directives in generate files.

- If the source name is long enough, clang-format can want to reflow that
  comment line, so move up the directive.
- Fix typo at the end of the file.
diff --git a/objectivec/GPBTimestamp.pbobjc.m b/objectivec/GPBTimestamp.pbobjc.m
index 1792ecb..7d2276c 100644
--- a/objectivec/GPBTimestamp.pbobjc.m
+++ b/objectivec/GPBTimestamp.pbobjc.m
@@ -1,7 +1,6 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
-// source: google/protobuf/timestamp.proto
-
 // clang-format off
+// source: google/protobuf/timestamp.proto
 
 #import "GPBProtocolBuffers_RuntimeSupport.h"
 #import "GPBTimestamp.pbobjc.h"
@@ -96,4 +95,4 @@
 
 // @@protoc_insertion_point(global_scope)
 
-// clange-format on
+// clang-format on