docs: Remove remains of Mir backend

docs/reference/gtk/gtk4-docs.xml

@@ -385,7 +385,6 @@
     <xi:include href="osx.sgml" />
     <xi:include href="broadway.xml" />
     <xi:include href="wayland.xml" />
-    <xi:include href="mir.xml" />
   </part>
 
   <xi:include href="glossary.xml" />

docs/reference/gtk/meson.build

@@ -355,7 +355,6 @@ content_files = [
   'input-handling.xml',
   'migrating-2to4.xml',
   'migrating-3to4.xml',
-  'mir.xml',
   'osx.sgml',
   'other_software.sgml',
   'overview.xml',

docs/reference/gtk/mir.xml

@@ -1,35 +0,0 @@
-<?xml version="1.0"?>
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
-               "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
-]>
-<refentry id="gtk-mir">
-<refmeta>
-<refentrytitle>Using GTK+ with Mir</refentrytitle>
-<manvolnum>3</manvolnum>
-<refmiscinfo>GTK Library</refmiscinfo>
-</refmeta>
-
-<refnamediv>
-<refname>Using GTK+ with Mir</refname>
-<refpurpose>
-Mir-specific aspects of using GTK+
-</refpurpose>
-</refnamediv>
-
-<refsect1>
-<title>Using GTK+ with Mir</title>
-
-<para>
-The GDK Mir backend provides support for running GTK+ applications
-under Mir based display servers. To run your application in this way,
-select the Mir backend by setting <literal>GDK_BACKEND=mir</literal>.
-</para>
-
-<para>
-Currently, the Mir backend does not use any additional commandline
-options or environment variables.
-</para>
-
-</refsect1>
-
-</refentry>

docs/reference/gtk/running.sgml

@@ -435,11 +435,6 @@ nevertheless.
         <listitem><para>Selects the Wayland backend for connecting to Wayland display servers</para></listitem>
       </varlistentry>
 
-      <varlistentry>
-        <term>mir</term>
-        <listitem><para>Selects the Mir backend for connecting to Mir display servers</para></listitem>
-      </varlistentry>
-
     </variablelist>
     Since 3.10, this environment variable can contain a comma-separated list
     of backend names, which are tried in order. The list may also contain