Move -all flag usage from drop to down

[Juneezee]

The -all flag still exists for drop usage, even though the drop subcommand no longer accepts -all anymore.

[dhui]

The drop command still accepts the -all parameter

[Juneezee]

@dhui Using migrate v4.14.1, doing the following command

$ migrate -database 'postgresql://postgres:postgres@localhost:5432/db?sslmode=disable' -path migrations/ drop -all

returns the following output

flag provided but not defined: -all
Usage of drop:
  -f	Force the drop command by bypassing the confirmation prompt
  -help
    	Print help informatio

Looking at the source code for drop, it doesn't seem to accept -all flag anymore(?)

[dhui]

Oh sorry! For some reason I confused down and drop...