[ci skip] docfix .. < => ..< (#12981) [backport]

Author: timotheecour

doc/tut1.rst

@@ -645,7 +645,7 @@ is possible, and actually an idiom:
     :test: "nim c $1"
   proc printSeq(s: seq, nprinted: int = -1) =
     var nprinted = if nprinted == -1: s.len else: min(nprinted, s.len)
-    for i in 0 .. <nprinted:
+    for i in 0 ..< nprinted:
       echo s[i]
 
 If the procedure needs to modify the argument for the