spec: example shows wrong value for complex constant

Looks like a typo.
Fixes #7011.

R=golang-codereviews, r, bradfitz
CC=golang-codereviews
https://golang.org/cl/45350043

doc/go_spec.html

@@ -3929,7 +3929,7 @@ an untyped complex constant.
 
 <pre>
 const ic = complex(0, c)   // ic == 3.75i  (untyped complex constant)
-const iΘ = complex(0, Θ)   // iΘ == 1.5i   (type complex128)
+const iΘ = complex(0, Θ)   // iΘ == 1i     (type complex128)
 </pre>
 
 <p>