MDL-45599 Fix tiny grammatical errors in the plugin installer

admin/tool/installaddon/lang/en/tool_installaddon.php

@@ -53,7 +53,7 @@
 $string['remoterequestalreadyinstalled'] = 'There is a request to install plugin {$a->name} ({$a->component}) version {$a->version} from the Moodle plugins directory on this site. However, this plugin is <strong>already installed</strong> on the site.';
 $string['remoterequestconfirm'] = 'There is a request to install plugin <strong>{$a->name}</strong> ({$a->component}) version {$a->version} from the Moodle plugins directory on this site. If you continue, the plugin ZIP package will be downloaded for validation. Nothing will be installed yet.';
 $string['remoterequestinvalid'] = 'There is a request to install a plugin from the Moodle plugins directory on this site. Unfortunately the request is not valid and so the plugin cannot be installed.';
-$string['remoterequestpermcheck'] = 'There is a request to install plugin {$a->name} ({$a->component}) version {$a->version} from the Moodle plugins directory on this site. However, the plugin type location <strong>{$a->typepath}</strong> is <strong>not writable</strong>. You need to give write access for the web server user to the plugin type location, then press the continue button to repeat the check.';
+$string['remoterequestpermcheck'] = 'There is a request to install plugin {$a->name} ({$a->component}) version {$a->version} from the Moodle plugins directory on this site. However, the location <strong>{$a->typepath}</strong> is <strong>not writable</strong>. You need to give write access for the web server user to the location, then press the continue button to repeat the check.';
 $string['remoterequestpluginfoexception'] = 'Oops... An error occurred while trying to obtain information about the plugin {$a->name} ({$a->component}) version {$a->version}. The plugin cannot be installed. Turn debugging mode on to see details of the error.';
 $string['validation'] = 'Plugin package validation';
 $string['validationmsg_componentmatch'] = 'Full component name';
@@ -86,7 +86,7 @@
 $string['validationmsg_rootdirinvalid'] = 'Invalid plugin name';
 $string['validationmsg_rootdirinvalid_help'] = 'The name of the root directory in the ZIP package violates formal syntax requirements. Some ZIP packages, such as those generated by Github, may contain an incorrect root directory name. You need to fix the name of the root directory to match the plugin name.';
 $string['validationmsg_targetexists'] = 'Target location already exists';
-$string['validationmsg_targetexists_help'] = 'The directory that the plugin is to be installed to, must not exist yet.';
+$string['validationmsg_targetexists_help'] = 'The directory that the plugin is to be installed to must not yet exist.';
 $string['validationmsg_unknowntype'] = 'Unknown plugin type';
 $string['validationmsglevel_debug'] = 'Debug';
 $string['validationmsglevel_error'] = 'Error';