Remove "hash -v" from man page

[Tim Lee <progscriptclone@gmail.com>]

src/dash.1 mentions "hash -v":

  hash -rv command ...
      The shell maintains a hash table which remembers the locations of
      commands.  With no arguments whatsoever, the hash command prints
      out the contents of this table.  Entries which have not been
      looked at since the last cd command are marked with an asterisk;
      it is possible for these entries to be invalid.

      With arguments, the hash command removes the specified commands
      from the hash table (unless they are functions) and then locates
      them.  With the -v option, hash prints the locations of the com‐
      mands as it finds them.  The -r option causes the hash command to
      delete all the entries in the hash table except for functions.


However "hash -v" results in an error:

    $ hash -v
    sh: 1: hash: Illegal option -v

The source code [1] shows that only the "-r" option is available; there
is no "-v" option. If there is no "-v" option, then it should be removed
from the documentation.

[1]: https://git.kernel.org/pub/scm/utils/dash/dash.git/tree/src/exec.c#n266