remover 'static' of getCurrentBrowser method

Author: YauheniPo

src/main/java/com/github/markusbernhardt/seleniumlibrary/CustomRobotDriverElement.java

@@ -38,7 +38,7 @@ private static SeleniumLibrary getLibraryInstance() throws ScriptException {
         return (SeleniumLibrary) engine.get("instance");
     }
 
-    protected static WebDriver getCurrentBrowser() {
+    protected WebDriver getCurrentBrowser() {
         return b.getCurrentWebDriver();
     }