typos in doc, no code changes

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>

apps/files_external/lib/Config/SimpleSubstitutionTrait.php

@@ -1,6 +1,6 @@
 <?php
 /**
- * @copyright Copyright (c) 2018 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
  *
  * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
  *
@@ -31,7 +31,7 @@ namespace OCA\Files_External\Config;
  */
 trait SimpleSubstitutionTrait {
 	/**
-	 * @var string the placeholder without @ prefix
+	 * @var string the placeholder without $ prefix
 	 * @since 16.0.0
 	 */
 	private $placeholder;

apps/files_external/lib/Service/BackendService.php

@@ -4,6 +4,7 @@
  *
  * @author Morris Jobke <hey@morrisjobke.de>
  * @author Robin McCorkell <robin@mccorkell.me.uk>
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
  *
  * @license AGPL-3.0
  *
@@ -292,8 +293,8 @@ class BackendService {
 	 *
 	 * The function of the provided $placeholder is mostly to act a sorting
 	 * criteria, so longer placeholders are replaced first. This avoids
-	 * "@user" overwriting parts of "@userMail" and "@userLang", for example.
-	 * The provided value should not contain the @ prefix, only a-z0-9 are
+	 * "$user" overwriting parts of "$userMail" and "$userLang", for example.
+	 * The provided value should not contain the $ prefix, only a-z0-9 are
 	 * allowed. Upper case letters are lower cased, the replacement is case-
 	 * insensitive.
 	 *

apps/files_external/lib/config.php

@@ -3,6 +3,7 @@
  * @copyright Copyright (c) 2016, ownCloud, Inc.
  *
  * @author Andreas Fischer <bantu@owncloud.com>
+ * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
  * @author Bart Visscher <bartv@thisnet.nl>
  * @author Björn Schießle <bjoern@schiessle.org>
  * @author Frank Karlitschek <frank@karlitschek.de>

apps/files_external/tests/Config/UserPlaceholderHandlerTest.php

@@ -1,6 +1,6 @@
 <?php
 /**
- * @copyright Copyright (c) 2018 Arthur Schiwon <blizzz@arthur-schiwon.de>
+ * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
  *
  * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
  *

apps/files_external/tests/Service/BackendServiceTest.php

@@ -220,6 +220,7 @@ class BackendServiceTest extends \Test\TestCase {
 	public function invalidConfigPlaceholderProvider() {
 		return [
 			[['@user']],
+			[['$user']],
 			[['hællo']],
 			[['spa ce']],
 			[['yo\o']],