Trim trailing whitespace.

Changes-By: lintian-brush
Fixes: lintian: trailing-whitespace
See-also: https://lintian.debian.org/tags/trailing-whitespace.html

debian/changelog

@@ -66,7 +66,7 @@ poppler (21.06.0-1) experimental; urgency=medium
 poppler (21.02.0-1) experimental; urgency=medium
 
   * New upstream version, updated for the soname change
-  * debian/control: 
+  * debian/control:
     - build-depends on libgdk-pixbuf-2.0-dev and libgtk-3-dev
     - updated standards version
   * debian/libpoppler-dev.install: