runtime/pprof: fix spelling in test

Change-Id: Id10e41fe396156106f63a4b29d673b31bea5358f
Reviewed-on: https://go-review.googlesource.com/34551Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/pprof/pprof_test.go

@@ -207,7 +207,7 @@ func profileOk(t *testing.T, need []string, prof bytes.Buffer, duration time.Dur
 	// We used to always require at least ideal/4 samples,
 	// but that is too hard to guarantee on a loaded system.
 	// Now we accept 10 or more samples, which we take to be
-	// enough to show that at least some profiling is ocurring.
+	// enough to show that at least some profiling is occurring.
 	if ideal := uintptr(duration * 100 / time.Second); samples == 0 || (samples < ideal/4 && samples < 10) {
 		t.Logf("too few samples; got %d, want at least %d, ideally %d", samples, ideal/4, ideal)
 		ok = false