Update dependency robotframework to v6

Author: renovate[bot]

requirements.txt

@@ -5,7 +5,7 @@ chardet==5.1.0
 idna==3.4
 lxml==4.9.2
 requests==2.28.2
-robotframework==4.1.3
+robotframework==6.0.2
 robotframework-pythonlibcore==2.2.1
 robotframework-selenium2library==3.0.0
 robotframework-seleniumlibrary==5.1.3