all: fix typos in documentation and translated strings

https://bugzilla.gnome.org/show_bug.cgi?id=770445

clients/common/nm-vpn-helpers.c

@@ -56,7 +56,7 @@ nm_vpn_get_editor_plugin (const char *service_type, GError **error)
 		if (   !nm_vpn_plugin_info_get_plugin (plugin_info)
 		    && nm_vpn_plugin_info_lookup_property (plugin_info, NM_VPN_PLUGIN_INFO_KF_GROUP_GNOME, "properties")) {
 			g_set_error (error, NM_VPN_PLUGIN_ERROR, NM_VPN_PLUGIN_ERROR_FAILED,
-			             _("cannot cannot load legacy-only VPN plugin \"%s\" for \"%s\""),
+			             _("cannot load legacy-only VPN plugin \"%s\" for \"%s\""),
 			             nm_vpn_plugin_info_get_name (plugin_info),
 			             nm_vpn_plugin_info_get_filename (plugin_info));
 		} else if (g_error_matches (local, G_FILE_ERROR, G_FILE_ERROR_NOENT)) {

libnm-core/nm-setting-ip6-config.h

@@ -127,7 +127,7 @@ typedef enum {
  * key along with the connection identification and the network address as
  * specified by RFC7217.
  *
- * #NMSettingIP6ConfigAddrGenMode controls how the the Interface Identifier for
+ * #NMSettingIP6ConfigAddrGenMode controls how the Interface Identifier for
  * RFC4862 Stateless Address Autoconfiguration is created.
  *
  * Since: 1.2

policy/org.freedesktop.NetworkManager.policy.in.in

@@ -134,7 +134,7 @@
 
   <action id="org.freedesktop.NetworkManager.checkpoint-rollback">
     <_description>Perform a checkpoint or rollback of interfaces configuration</_description>
-    <_message>System policy prevents the the creation of a checkpoint or its rollback</_message>
+    <_message>System policy prevents the creation of a checkpoint or its rollback</_message>
     <defaults>
       <allow_any>auth_admin_keep</allow_any>
       <allow_inactive>auth_admin_keep</allow_inactive>