docs: fix typo

Remove an errant "-" in a sample script.  Thanks to Terence Brouns for
pointing out the issue.

Signed-off-by: Jeff Squyres <jeff@squyres.com>

Author: jsquyres

docs/getting-help.rst

@@ -120,7 +120,7 @@ information (adjust as necessary for your specific environment):
    # Fill in the options you want to pass to configure here
    options=""
    ./configure $options 2>&1  | tee $dir/config.out
-   tar -cf - `find . -name config.log` | tar -x -C $dir -
+   tar -cf - `find . -name config.log` | tar -x -C $dir
 
    # Build and install Open MPI
    make V=1 all 2>&1          | tee $dir/make.out