README: remove references to backports.lzma

Now that this is python3 only, we always have lzma

README.rst

@@ -72,10 +72,6 @@ If you are running from repository, you need to fetch them first::
 
   python setup.py deps
 
-Also, apachedex can make use of backports.lzma
-(http://pypi.python.org/pypi/backports.lzma/) if it's installed to support xz
-file compression.
-
 Input
 -----
 
@@ -92,7 +88,7 @@ Input files may be provided uncompressed or compressed in:
 
 - gzip2
 
-- xz (if module backports.lzma is installed)
+- xz
 
 Input filename "-" is understood as stdin.