Put back the [compat] section of Project.toml as it was in version 1.15 (#110)

Author: rrsadykov

Project.toml

@@ -12,12 +12,12 @@ MetaGraphs = "626554b9-1ddb-594c-aa3c-2596fe9399a5"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [compat]
-Combinatorics = "1"
-Graphs = "^1.7"
-MetaGraphs = ">= 0.7, < 0.9"
-julia = "^1.6"
+Combinatorics = "1.0.2"
+Graphs = "~1.7, 1.8"
 JuMP = "^1.2"
 MathOptInterface = "1"
+MetaGraphs = "~0.7"
+julia = "1.6"
 
 [extras]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"