Fix a typo in surf manual.

`Ctrl-/` displays incorrectly in `man surf` on my machine.

A patch is attached.

(You also access it here:
https://github.com/weakish/surf/commit/07e97eccedd96eabf14b2fbf77de75ec1b594d97)

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 surf.1 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Signed-off-by: Christoph Lohmann <20h@r-36.net>