Remove the git.paging.useConfig option

Many people don't understand what this means, which is apparent from the amount
of issues that got filed because of this. Let's get rid of it to avoid this
confusion. People will have to configure their pager twice if they want to use
it both on the command line and in lazygit, which I think is not a big deal.

docs/Config.md

@@ -303,9 +303,6 @@ git:
     # ydiff -p cat -s --wrap --width={{columnWidth}}
     pager: ""
 
-    # If true, Lazygit will use whatever pager is specified in `$GIT_PAGER`, `$PAGER`, or your *git config*. If the pager ends with something like ` | less` we will strip that part out, because less doesn't play nice with our rendering approach. If the custom pager uses less under the hood, that will also break rendering (hence the `--paging=never` flag for the `delta` pager).
-    useConfig: false
-
     # e.g. 'difft --color=always'
     externalDiffCommand: ""