build: remove outdated, commented-out configure.ac snippet

This was likely added during the port to meson. It's just a multiline
string, so it has no effect in meson, and it appears to be entirely for
things which are already implemented in meson, so there's no real point
in keeping it any longer.

meson.build

@@ -963,38 +963,6 @@ data_conf.set('nmstatedir',                              nm_pkgstatedir)
 data_conf.set('sbindir',                                 nm_sbindir)
 data_conf.set('sysconfdir',                              nm_sysconfdir)
 
-# check if we can build setting property documentation
-'''
-build_docs=no
-if test -n "$INTROSPECTION_MAKEFILE"; then
-  # If g-i is installed we know we have python, but we might not have pygobject
-  if ! "$PYTHON" -c 'from gi.repository import GObject' >& /dev/null; then
-    AC_MSG_ERROR(["--enable-introspection aims to build the settings documentation. This requires GObject introspection for python (pygobject)])
-  fi
-
-  AC_PATH_PROG(PERL, perl)
-  if test -z "$PERL"; then
-    AC_MSG_ERROR([--enable-introspection requires perl])
-  fi
-  AC_PATH_PROG(XSLTPROC, xsltproc)
-  if test -z "$XSLTPROC"; then
-    AC_MSG_ERROR([--enable-introspection requires xsltproc])
-  fi
-
-  have_introspection=yes
-  if test "$enable_gtk_doc" = "yes"; then
-    build_docs=yes
-  fi
-else
-  if test "$enable_gtk_doc" = "yes"; then
-    # large parts of the documentation require introspection/pygobject to extract
-    # the documentation out of the source files. You cannot enable gtk-doc without alone.
-    AC_MSG_ERROR(["--with-gtk-doc requires --enable-introspection"])
-  fi
-  have_introspection=no
-fi
-'''
-
 content_files = []
 
 subdir('introspection')