gnu: icecat: Update to 31.1.1.

* gnu/packages/gnuzilla.scm (icecat): Update to 31.1.1.  Add 'pango',
  'freetype', 'libxft' and 'pulseaudio' as inputs.  Set
  'out-of-source?' to #t.  Remove 'sanitise' phase.  Adapt customized
  'configure' phase to handle 'out-of-source?' build.  Add
  '--with-l10n-base' argument to configure.