runtime: fix typo in gdb script

Change-Id: I9d4b3e25b00724f0e4870c6082671b4f14cc18fc
Reviewed-on: https://go-review.googlesource.com/100463
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/runtime-gdb.py

@@ -445,7 +445,7 @@ class GoroutinesCmd(gdb.Command):
 def find_goroutine(goid):
 	"""
 	find_goroutine attempts to find the goroutine identified by goid.
-	It returns a touple of gdv.Value's representing the stack pointer
+	It returns a tuple of gdv.Value's representing the stack pointer
 	and program counter pointer for the goroutine.
 
 	@param int goid