CompatHelper: bump compat for GraphPlot in [weakdeps] to 0.6, (keep existing compat)

Author: CompatHelper Julia

Project.toml

@@ -31,7 +31,7 @@ DataStructures = "0.18"
 Dictionaries = "0.4"
 Distributions = "0.25"
 Documenter = "1.0"
-GraphPlot = "0.5"
+GraphPlot = "0.5, 0.6"
 MacroTools = "0.5"
 MetaGraphsNext = "0.6, 0.7"
 NamedTupleTools = "0.14"