Documentation: remove extra quoting/emphasis around literal texts

Documentation: remove extra quoting/emphasis around literal texts

If literal text (asciidoc `...`) can be rendered in a differently from
normal text for each output format (man, HTML), then we do not need
extra quotes or other wrapping around inline literal text segments.

config.txt

  Change '`...`' to `...`. In asciidoc, the single quotes provide
  emphasis, literal text should be distintive enough.

  Change "`...`" to `...`. These double quotes do not work if present
  in the described config value, so drop them.

git-checkout.txt

  Change "`...`" to `...` or `"..."`. All instances are command line
  argument examples. One "`-`" becomes `-`. Two others are involve
  curly braces, so move the double quotes inside the literal region to
  indicate that they might need to be quoted on the command line of
  certain shells (tcsh).

git-merge.txt

  Change "`...`" to `...`. All instances are used to describe merge
  conflict markers. The quotes should are not important.

git-rev-parse.txt

  Change "`...`" to `...`. All instances are around command line
  arguments where no in-shell quoting should be necessary.

gitcli.txt

  Change `"..."` to `...`. All instances are around command line
  examples or single command arguments. They do not semanticly belong
  inside the literal text, and they are not needed outside it.

glossary-content.txt
user-manual.txt

  Change "`...`" to `...`. All instances were around command lines.

Signed-off-by: Chris Johnsen <chris_johnsen@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>