fix misspell

Author: lezhnev74

src/spec/Parameter.php

@@ -118,7 +118,7 @@ protected function performValidation()
             $this->addError('A Parameter Object MUST contain either a schema property, or a content property, but not both.');
         }
         if (! empty($this->content) && count($this->content) !== 1) {
-            $this->addError('A Parameter Object MUST with Content property must have A SINGLE content type.');
+            $this->addError('A Parameter Object with Content property MUST have A SINGLE content type.');
         }
 
         $supportedSerializationStyles = [

tests/spec/ParameterTest.php

@@ -186,7 +186,7 @@ public function testItValidatesContentCanHaveOnlySingleKey()
             , Parameter::class);
 
         $result = $parameter->validate();
-        $this->assertEquals(['A Parameter Object MUST with Content property must have A SINGLE content type.'], $parameter->getErrors());
+        $this->assertEquals(['A Parameter Object with Content property MUST have A SINGLE content type.'], $parameter->getErrors());
         $this->assertFalse($result);
     }