ORC-1120: Remove C++ library limitation about write version (#1054)

### What changes were proposed in this pull request?

Delete the content in README.md which states the cpp writer only writes 0.11 version.

### Why are the changes needed?

Inconsistency between doc and code.

### How was this patch tested?

Manually check the README.md file under root directory.

README.md

@@ -15,7 +15,7 @@ lists, maps, and unions.
 
 ## ORC File Library
 
-This project includes both a Java library and a C++ library for reading and writing the _Optimized Row Columnar_ (ORC) file format. The C++ and Java libraries are completely independent of each other and will each read all versions of ORC files. But the C++ library only writes the original (Hive 0.11) version of ORC files, and will be extended in the future.
+This project includes both a Java library and a C++ library for reading and writing the _Optimized Row Columnar_ (ORC) file format. The C++ and Java libraries are completely independent of each other and will each read all versions of ORC files.
 
 Releases:
 * Latest: <a href="http://orc.apache.org/releases">Apache ORC releases</a>