content: fix line numbers on output of Timer.Reset example

From perspective of someone who may not or may have an experience on
having race conditions, the line number "15" a little bit off because it
does not have any reference to variable `t`.
Especially when the next paragraph said "The race detector shows the
problem: an unsynchronized read and write of the variable t".

This changes not only fix the line number "15", but also make it
consistent with actual output (although its run on Go tip not Go 1.1),

----
% go run -race race.go
950.434733ms
==================
WARNING: DATA RACE
Read at 0x00c00013e018 by goroutine 8:
  main.main.func1()
      race.go:14 +0x126

Previous write at 0x00c00013e018 by main goroutine:
  main.main()
      race.go:12 +0x194

Goroutine 8 (running) created at:
  time.goFunc()
      .../share/go/src/time/sleep.go:169 +0x51
==================
1.037465812s
1.706961927s
...
----

the read conflict is on `func 001` (line number 16 on example) and write
conflict is on main (line number 14 on example).

Change-Id: I3b9a7880178845d8dc4dff38e197fc3eef407e58
Reviewed-on: https://go-review.googlesource.com/c/blog/+/280712
Reviewed-by: Andrew Gerrand <adg@golang.org>

content/race-detector.article

@@ -105,11 +105,11 @@ What's going on here? Running the program with the race detector enabled is more
 	WARNING: DATA RACE
 	Read by goroutine 5:
 	  main.func·001()
-	     race.go:14 +0x169
+	     race.go:16 +0x169
 
 	Previous write by goroutine 1:
 	  main.main()
-	      race.go:15 +0x174
+	      race.go:14 +0x174
 
 	Goroutine 5 (running) created at:
 	  time.goFunc()