Fix RLEnv version

Author: jeremiahpslewis

src/ReinforcementLearningEnvironments/Project.toml

@@ -24,10 +24,10 @@ IntervalSets = "0.7"
 MacroTools = "0.5"
 OpenSpiel = "0.2.1"
 ReinforcementLearningBase = "0.12"
-ReinforcementLearningCore = "0.12, 0.13, 0.14, 0.15"
+ReinforcementLearningCore = "0.13"
 Requires = "1.0"
 StatsBase = "0.32, 0.33, 0.34"
-julia = "1.3"
+julia = "1.6"
 
 [extras]
 ArcadeLearningEnvironment = "b7f77d8d-088d-5e02-8ac0-89aab2acc977"