Update slevomat/coding-standard and remove unavailable sniff (#2)

Author: Ethan Bray

composer.json

@@ -4,7 +4,7 @@
     "description": "MessageCloud Coding Standard",
     "require": {
         "squizlabs/php_codesniffer": "^3.0",
-        "slevomat/coding-standard": "^4.6",
+        "slevomat/coding-standard": "^5.0",
         "dealerdirect/phpcodesniffer-composer-installer": "^0.4.4"
     },
     "require-dev": {

ruleset.xml

@@ -231,7 +231,4 @@
 
     <!-- Forbid useless alias for classes, constants and functions -->
     <rule ref="SlevomatCodingStandard.Namespaces.UselessAlias"/>
-
-    <!-- Require /* @var type $foo */ and similar simple inline annotations to be replaced by assert() -->
-    <rule ref="SlevomatCodingStandard.PHP.RequireExplicitAssertion"/>
 </ruleset>