Remove deprecated git-up configuration and port it across to the current 'up' alias

config/git/config

@@ -8,7 +8,7 @@
 	co = checkout
 	d = diff
 	l = log --graph --pretty=graph --date=relative
-	up = pull --rebase --autostash
+	up = pull --rebase=preserve --autostash
 	st = status --short
 	shove = "!f() { git push ${1:-origin} :; }; f"
 
@@ -21,9 +21,6 @@
 	process = git-lfs filter-process
 	required = true
 
-[git-up.rebase]
-	arguments = --preserve-merges
-
 [gpg]
 	program = gpg-for-git-signing