Bump fortran-curl version to 0.6.0 (#59)

Author: milancurcic

fpm.toml

@@ -19,5 +19,5 @@ implicit-external = false
 source-form = "free"
 
 [dependencies]
-fortran-curl = {git = "https://github.com/interkosmos/fortran-curl.git", tag = "0.5.0"}
-stdlib = "*"
+fortran-curl = {git = "https://github.com/interkosmos/fortran-curl.git", tag = "0.6.0"}
+stdlib = "*"