HDFS-14213. Remove Jansson from BUILDING.txt. Contributed by Dinesh Chitlangia.

(cherry picked from commit 96a84b61fb693e9657f1f1ae3d6ed3a04a7e8efa)

BUILDING.txt

@@ -14,7 +14,6 @@ Requirements:
   Clang (community version), Clang (version for iOS 9 and later) (if compiling native code)
 * openssl devel (if compiling native hadoop-pipes and to get the best HDFS encryption performance)
 * Linux FUSE (Filesystem in Userspace) version 2.6 or above (if compiling fuse_dfs)
-* Jansson C XML parsing library ( if compiling libwebhdfs )
 * Doxygen ( if compiling libhdfspp and generating the documents )
 * Internet connection for first build (to fetch all Maven and Hadoop dependencies)
 * python (for releasedocs)
@@ -83,8 +82,6 @@ Optional packages:
   (OR https://github.com/01org/isa-l)
 * Bzip2
   $ sudo apt-get install bzip2 libbz2-dev
-* Jansson (C Library for JSON)
-  $ sudo apt-get install libjansson-dev
 * Linux FUSE
   $ sudo apt-get install fuse libfuse-dev
 * ZStandard compression