bump julia compat to "1.4"

to match the compat of `PlotlyBase.jl` (one of our deps)

Author: etpinard

Project.toml

@@ -36,8 +36,8 @@ JSON3 = "1.9"
 MD5 = "0.2"
 PlotlyBase = "0.8.5, 0.8.6"
 YAML = "0.4.7"
-julia = "1.3"
 Requires = "1.3"
+julia = "1.4"
 
 [extras]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"