avoid removing '@param mixed' for compatibility with php-cs-fix version used in PHP 7.3

Author: fain182

.php-cs-fixer.dist.php

@@ -24,6 +24,7 @@
         'modernize_types_casting' => true, // Replaces intval, floatval, doubleval, strval and boolval function calls with according type casting operator.
         'multiline_whitespace_before_semicolons' => true, // Forbid multi-line whitespace before the closing semicolon or move the semicolon to the new line for chained calls.
         'no_unreachable_default_argument_value' => true, // In function arguments there must not be arguments with default values before non-default ones.
+	'no_superfluous_phpdoc_tags' => ['allow_mixed' => true],// To avoid problems of compatibility with the old php-cs-fixer version used on PHP 7.3
         'no_useless_else' => true,
         'no_useless_return' => true,
         'ordered_class_elements' => true, // Orders the elements of classes/interfaces/traits.