core-tutorial: http reference link fix

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/core-tutorial.txt

@@ -1469,8 +1469,8 @@ Working with Others
 Although git is a truly distributed system, it is often
 convenient to organize your project with an informal hierarchy
 of developers. Linux kernel development is run this way. There
-is a nice illustration (page 17, "Merges to Mainline") in Randy
-Dunlap's presentation (`http://tinyurl.com/a2jdg`).
+is a nice illustration (page 17, "Merges to Mainline") in
+link:http://tinyurl.com/a2jdg[Randy Dunlap's presentation].
 
 It should be stressed that this hierarchy is purely *informal*.
 There is nothing fundamental in git that enforces the "chain of