Remove unused variables from a few sniffs (#2514)

* Remove unused variable passed as the third parameter to `preg_match()`

This commit removes three instances where a variable was passed to
`preg_match()` as the third parameter to fill it with the results of the
search, but later it was not used.

* EscapeOutput: remove unused variable `$end`

This commit removes the unnecessary initialization of the variable
`$end` at the beginning of the sniff code. Every single `case` statement
of the `switch` that follows either re-initialize the variable with a
different value or returns without using the variable.

WordPress/Sniffs/Security/EscapeOutputSniff.php

@@ -185,7 +185,6 @@ public function getGroups() {
 	 */
 	public function process_token( $stackPtr ) {
 		$start = ( $stackPtr + 1 );
-		$end   = $start;
 
 		switch ( $this->tokens[ $stackPtr ]['code'] ) {
 			case \T_STRING:

WordPress/Sniffs/WP/I18nSniff.php

@@ -873,7 +873,7 @@ private function check_for_translator_comment( $stackPtr, $matched_content, $par
 				continue;
 			}
 
-			if ( preg_match( self::SPRINTF_PLACEHOLDER_REGEX, $param_info['clean'], $placeholders ) === 1 ) {
+			if ( preg_match( self::SPRINTF_PLACEHOLDER_REGEX, $param_info['clean'] ) === 1 ) {
 				$needs_translators_comment = true;
 				break;
 			}
@@ -969,7 +969,7 @@ private function check_for_translator_comment( $stackPtr, $matched_content, $par
 	 * @return bool
 	 */
 	private function is_translators_comment( $content ) {
-		if ( preg_match( '`^(?:(?://|/\*{1,2}) )?translators:`i', $content, $matches ) === 1 ) {
+		if ( preg_match( '`^(?:(?://|/\*{1,2}) )?translators:`i', $content ) === 1 ) {
 			return true;
 		}
 		return false;

WordPress/Sniffs/WhiteSpace/ControlStructureSpacingSniff.php

@@ -410,7 +410,7 @@ public function process_token( $stackPtr ) {
 
 			// Move past end comments.
 			if ( $this->tokens[ $trailingContent ]['line'] === $this->tokens[ $scopeCloser ]['line'] ) {
-				if ( preg_match( '`^//[ ]?end`i', $this->tokens[ $trailingContent ]['content'], $matches ) > 0 ) {
+				if ( preg_match( '`^//[ ]?end`i', $this->tokens[ $trailingContent ]['content'] ) > 0 ) {
 					$scopeCloser     = $trailingContent;
 					$trailingContent = $this->phpcsFile->findNext( \T_WHITESPACE, ( $trailingContent + 1 ), null, true );
 				}