fix(flowchart): apply ELK mergeEdges in subgraphs#7703

ptlnextdoor wants to merge 2 commits into

mermaid-js:developmermaid-js/mermaid:developfrom

ptlnextdoor:bug/7659_flowchart-elk-merge-edges-subgraphsptlnextdoor/mermaid:bug/7659_flowchart-elk-merge-edges-subgraphsCopy head branch name to clipboard