remove saveDFG compress keyword

Author: dehann

src/FileDFG/services/FileDFG.jl

@@ -17,11 +17,7 @@ v1 = addVariable!(dfg, :a, ContinuousScalar, labels = [:POSE], solvable=0)
 saveDFG(dfg, "/tmp/saveDFG.tar.gz")
 ```
 """
-function saveDFG(dfg::AbstractDFG, folder::String; compress::Symbol=:null)
-
-    if compress != :null
-      @warn "saveDFG keyword args are deprecated, and folders will be tarred as standard in current and future versions."
-    end
+function saveDFG( dfg::AbstractDFG, folder::String )
 
     # TODO: Deprecate the folder functionality in v0.6.1