now requires at least OCaml 4.08.0

Author: backtracking

CHANGES.md

@@ -1,6 +1,7 @@
 
 # 2.1.0 (August 30, 2023)
 
+  - :exclamation: OCamlGraph now requires OCaml >= 4.08
   - :exclamation: [Traverse]: fixed [Dfs.fold] and [Dfs.fold_component],
     which were not implementing a proper DFS
   - [Classic]: new functions [cycle] and [grid]

ocamlgraph_gtk.opam

@@ -18,7 +18,7 @@ homepage: "https://github.com/backtracking/ocamlgraph/"
 doc: "https://backtracking.github.io/ocamlgraph"
 bug-reports: "https://github.com/backtracking/ocamlgraph/issues/new"
 depends: [
-  "ocaml" {>= "4.03.0"}
+  "ocaml" {>= "4.08.0"}
   "stdlib-shims"
   "lablgtk"
   "conf-gnomecanvas"