[FLINK-18917] Add a "Built-in Functions" link (linked to dev/table/functions/systemFunctions.md) under the "Python API" -> "User Guide" -> "Table API" section

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.11.2, 1.12.0
• Component/s: Documentation
• Labels: pull-request-available
• Assignee: Wei Zhong
• Reporter: Wei Zhong
• Created: 13/Aug/20 06:26
• Updated: 27/Aug/20 02:19
• Resolved: 27/Aug/20 02:19

Issue Links

• links to: GitHub Pull Request #13226