fix(comp): Fix broken completion for --output flag

For commands using the new post-render flag, the completion for the
--output flag was broken.

For example:
   helm install -o <TAB>
   __helm_handle_reply:47: command not found: __helm_output_options

The bash __helm_output_options function is no longer used but was
referred to by mistake.

This commit removes the offending code.

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>
(cherry picked from commit 023bdaec63)

cmd/helm/flags.go

@@ -99,8 +99,6 @@ func (o *outputValue) Set(s string) error {
 
 func bindPostRenderFlag(cmd *cobra.Command, varRef *postrender.PostRenderer) {
 	cmd.Flags().Var(&postRenderer{varRef}, postRenderFlag, "the path to an executable to be used for post rendering. If it exists in $PATH, the binary will be used, otherwise it will try to look for the executable at the given path")
-	// Setup shell completion for the flag
-	cmd.MarkFlagCustom(outputFlag, "__helm_output_options")
 }
 
 type postRenderer struct {