[nautilus] extension: Bump extensiondir to 4

[António Fernandes <antoniof src gnome org>]

commit d97f112734a949a6826d09c1d3fc58990273f2e6
Author: Jeremy Bicha <jeremy bicha canonical com>
Date:   Sun Aug 7 10:08:06 2022 -0400

    extension: Bump extensiondir to 4
    
    Closes: https://gitlab.gnome.org/GNOME/nautilus/-/issues/2417

 libnautilus-extension/meson.build | 2 --
 meson.build                       | 4 +++-
 2 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/libnautilus-extension/meson.build b/libnautilus-extension/meson.build
index b30b8561f..457166993 100644
--- a/libnautilus-extension/meson.build
+++ b/libnautilus-extension/meson.build
@@ -1,5 +1,3 @@
-nautilus_extension_version = '4'
-
 libnautilus_extension_headers = [
   'nautilus-column-provider.h',
   'nautilus-column.h',
diff --git a/meson.build b/meson.build
index 735dd50cc..a1e5b7144 100644
--- a/meson.build
+++ b/meson.build
@@ -9,6 +9,8 @@ project('nautilus', 'c',
   license: 'GPL-3.0-or-later'
 )
 
+nautilus_extension_version = '4'
+
 ###############
 # Directories #
 ###############
@@ -21,7 +23,7 @@ desktopdir = join_paths(datadir, 'applications')
 includedir = get_option('includedir')
 libdir = get_option('libdir')
 localedir = get_option('localedir')
-extensiondir = join_paths(libdir, 'nautilus', 'extensions-3.0')
+extensiondir = join_paths(libdir, 'nautilus', 'extensions-' + nautilus_extension_version)
 servicedir = join_paths(datadir, 'dbus-1', 'services')
 
 ###################