Notion connector: unsupported block types crashes ingest

[EdmundKorley]

This is related to issue #1053 and the fix #1059.

We have seen that Notion connector ingest crashes when it tried to get the children of a specific block.

Hitting the Notion API directly shows that this is a special unsupported block type (may have replaced the ai_block which is not in Notion docs but not 100% sure). The connector should at least also skip processing unsupported block types.