math/rand/v2: drop pointer receiver on zero-width type

Just a cleanup.

Change-Id: Ibeb2c7d447c793086280e612fe5f0f7eeb863f71
Reviewed-on: https://go-review.googlesource.com/c/go/+/582875
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Damien Neil <[email protected]>
Reviewed-by: Jorropo <[email protected]>

Author: bradfitz

src/math/rand/v2/rand.go

@@ -253,15 +253,15 @@ func (r *Rand) Shuffle(n int, swap func(i, j int)) {
 
 // globalRand is the source of random numbers for the top-level
 // convenience functions.
-var globalRand = &Rand{src: &runtimeSource{}}
+var globalRand = &Rand{src: runtimeSource{}}
 
 //go:linkname runtime_rand runtime.rand
 func runtime_rand() uint64
 
 // runtimeSource is a Source that uses the runtime fastrand functions.
 type runtimeSource struct{}
 
-func (*runtimeSource) Uint64() uint64 {
+func (runtimeSource) Uint64() uint64 {
 	return runtime_rand()
 }