libutils: remove whitespace from String8 files

Remove trailing whitespace from String8 header and
cpp files.

BUG: None
Change-Id: Ie77da3f0fbce9cdce20225ce1310cf62295179a4
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index 771d312..ad45282 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -362,7 +362,7 @@
 status_t String8::real_append(const char* other, size_t otherLen)
 {
     const size_t myLen = bytes();
-    
+
     SharedBuffer* buf = SharedBuffer::bufferFromData(mString)
         ->editResize(myLen+otherLen+1);
     if (buf) {