Merge #6018

6018: Correct project_root path for ProjectJson. r=jonas-schievink a=woody77

It was already the folder containing the rust-project.json file, not the file itself.  This also removes the Option-ness of it, since it's now an infallible operation to set the member value.

Co-authored-by: Aaron Wood <aaronwood@google.com>

crates/rust-analyzer/src/reload.rs

@@ -252,7 +252,7 @@ impl GlobalState {
                     // Enable flychecks for json projects if a custom flycheck command was supplied
                     // in the workspace configuration.
                     match config {
-                        FlycheckConfig::CustomCommand { .. } => project.path(),
+                        FlycheckConfig::CustomCommand { .. } => Some(project.path()),
                         _ => None,
                     }
                 }