[java] Avoid checking for non W3C twice.

And `safari.options` is not a thing since
a while ago.

java/src/org/openqa/selenium/MutableCapabilities.java

@@ -37,7 +37,6 @@ public class MutableCapabilities implements Capabilities {
     keys.add("moz:firefoxOptions");
     keys.add("operaOptions");
     keys.add("se:ieOptions");
-    keys.add("safari.options");
     OPTION_KEYS = Collections.unmodifiableSet(keys);
   }
 
@@ -88,8 +87,6 @@ public void setCapability(String capabilityName, Platform value) {
   public void setCapability(String key, Object value) {
     Require.nonNull("Capability name", key);
 
-    W3CCapabilityKeysValidator.validateCapability(key);
-
     // We have to special-case some keys and values because of the popular idiom of calling
     // something like "capabilities.setCapability(SafariOptions.CAPABILITY, new SafariOptions());"
     // and this is no longer needed as options are capabilities. There will be a large amount of