update gradle versions

Author: hauner

src/testInt/groovy/io/openapiprocessor/gradle/support/Gradle.groovy

@@ -11,7 +11,8 @@ class Gradle {
         '7.0', '7.0.1', '7.0.2',
         '7.1', '7.1.1',
         '7.2',
-        '7.3', '7.3.1', '7.3.2', '7.3.3'
+        '7.3', '7.3.1', '7.3.2', '7.3.3',
+        '7.4', '7.4.1'
     ]
 
 }