docs: fix formatting and grammar

docs: fix formatting and grammar

When compiling the documentation, asciidoc thinks a backtick surrounded
by whitespace shouldn't be interpreted as marking the start or end of a
literal.  In most cases, that's useful behaviour, but in the git-pull
documentation it means asciidoc is failing to correctly detect which
text should be monospaced and which shouldn't.

To avoid this, remove the extraneous spaces from the text to be
monospaced.  It would also be possible to fix the formatting by
switching to asciidoc's ++ monospace format markers and still have the
space characters included in the monospace text, but the spaces aren't
necessary and not having them keeps the markup simpler.

Also include a minor grammar fix suggested by Jeff while we're changing
these lines.

Signed-off-by: Adam Dinwoodie <adam@dinwoodie.org>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>