CompatHelper: add new compat entry for "Gadfly" at version "1.1"

Author: github-actions[bot]

Project.toml

@@ -66,6 +66,7 @@ DifferentialEquations = "6.8"
 Distributions = "0.21"
 DoubleFloats = "0.9, 1.0"
 ForwardDiff = "0.10"
+Gadfly = "1.1"
 IJulia = "1.20"
 Latexify = "0.12"
 Measurements = "2.1"