math/cmpx: change space to tab in the Pow docs for better formatting

Godoc makes it look better this way; before, it all ran together into nonsense.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/90400045

src/pkg/math/cmplx/pow.go

@@ -44,8 +44,8 @@ import "math"
 
 // Pow returns x**y, the base-x exponential of y.
 // For generalized compatiblity with math.Pow:
-// Pow(0, ±0) returns 1+0i
-// Pow(0, c) for real(c)<0 returns Inf+0i if imag(c) is zero, otherwise Inf+Inf i.
+//	Pow(0, ±0) returns 1+0i
+//	Pow(0, c) for real(c)<0 returns Inf+0i if imag(c) is zero, otherwise Inf+Inf i.
 func Pow(x, y complex128) complex128 {
 	if x == 0 { // Guaranteed also true for x == -0.
 		r, i := real(y), imag(y)