Rollup merge of #60741 - shiatsumat:patch-let-mut-write-graph-label, r=varkor
Rollup merge of #60741 - shiatsumat:patch-let-mut-write-graph-label, r=varkor

Remove redundant "let mut" in write_graph_label

Removed the redundant "let mut" in the write_graph_label function (it caused "let mut let mut" for non-user-defined local variables).

aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust