Delete deprecated g: prefix in fucntion names (vim config)

g: prefix forbidden in newer version of Vim:

:fu[nction][!] {name}([arguments]) [range] [abort] [dict]
                        Define a new function by the name {name}.  The name
                        must be made of alphanumeric characters and '_', and
                        must start with a capital or "s:" (see above).  Note
                        that using "b:" or "g:" is not allowed. (since patch
                        7.4.260 E884 is given if the function name has a colon
                        in the name, e.g. for "foo:bar()".  Before that patch
                        no error was given).