Documentation/config/checkout: replace sq with backticks

The modern style for Git documentation is to use backticks to quote
any command-line documenation so that it is typeset in monospace.
Replace all single quotes with backticks to conform to this.

Signed-off-by: Denton Liu <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Denton-L

Documentation/config/checkout.txt

@@ -1,18 +1,18 @@
 checkout.defaultRemote::
-	When you run 'git checkout <something>'
-	or 'git switch <something>' and only have one
+	When you run `git checkout <something>`
+	or `git switch <something>` and only have one
 	remote, it may implicitly fall back on checking out and
-	tracking e.g. 'origin/<something>'. This stops working as soon
-	as you have more than one remote with a '<something>'
+	tracking e.g. `origin/<something>`. This stops working as soon
+	as you have more than one remote with a `<something>`
 	reference. This setting allows for setting the name of a
 	preferred remote that should always win when it comes to
 	disambiguation. The typical use-case is to set this to
 	`origin`.
 +
 Currently this is used by linkgit:git-switch[1] and
-linkgit:git-checkout[1] when 'git checkout <something>'
-or 'git switch <something>'
-will checkout the '<something>' branch on another remote,
-and by linkgit:git-worktree[1] when 'git worktree add' refers to a
+linkgit:git-checkout[1] when `git checkout <something>`
+or `git switch <something>`
+will checkout the `<something>` branch on another remote,
+and by linkgit:git-worktree[1] when `git worktree add` refers to a
 remote branch. This setting might be used for other checkout-like
 commands or functionality in the future.