Fix "customer timer" -> "custom timer" (reported by Kirk Strauser on docs@)
diff --git a/Doc/library/profile.rst b/Doc/library/profile.rst
index 00abef2..0fb1489 100644
--- a/Doc/library/profile.rst
+++ b/Doc/library/profile.rst
@@ -625,8 +625,8 @@
 
 .. _profile-timers:
 
-Using a customer timer
-======================
+Using a custom timer
+====================
 
 If you want to change how current time is determined (for example, to force use
 of wall-clock time or elapsed process time), pass the timing function you want