Dpkg::Compression: Fix the current default compressor in the documentation

debian/changelog

@@ -10,6 +10,8 @@ dpkg (1.18.1) UNRELEASED; urgency=low
     - Use non-destructive substitutions inside map.
     - Use the state keyword to simplify the code.
     - Do not replace #PACKAGE# in template mode in Dpkg::Shlibs::SymbolFile.
+  * Documentation:
+    - Update current default source compressor from gzip to xz.
 
   [ Updated programs translations ]
   * German (Sven Joachim).

scripts/Dpkg/Compression.pm

@@ -165,7 +165,7 @@ sub compression_get_file_extension_regex {
 
 =item my $comp = compression_get_default()
 
-Return the default compression method. It's "gzip" unless
+Return the default compression method. It is "xz" unless
 C<compression_set_default> has been used to change it.
 
 =item compression_set_default($comp)