[epiphany/mcatanzaro/postinstall] Remove legacy postinstall script

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 184e3cef76200fa099dba525c38e297ac4454b2f
Author: Michael Catanzaro <mcatanzaro redhat com>
Date:   Mon Jul 18 13:30:58 2022 -0500

    Remove legacy postinstall script
    
    Nowadays Meson has built-in support for this.

 meson.build     |  9 ++++++---
 post_install.py | 27 ---------------------------
 2 files changed, 6 insertions(+), 30 deletions(-)
---
diff --git a/meson.build b/meson.build
index 9d0d40364..2a55cd85a 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project('epiphany', 'c',
   license: 'GPL3+',
   version: '43.alpha',
-  meson_version: '>= 0.51.0',
+  meson_version: '>= 0.59.0',
   default_options: ['c_std=gnu11',
                     'warning_level=2']
 )
@@ -159,5 +159,8 @@ subdir('embed')
 subdir('src')
 subdir('tests')
 
-meson.add_install_script('post_install.py')
-
+gnome.post_install(
+  gtk_update_icon_cache: true,
+  glib_compile_schemas: true,
+  update_desktop_database: true
+)