runtime: fix typos

Change-Id: Iffc25fc80452baf090bf8ef15ab798cfaa120b8e
Reviewed-on: https://go-review.googlesource.com/16154Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/msan0.go

@@ -16,7 +16,7 @@ const msanenabled = false
 
 // Because msanenabled is false, none of these functions should be called.
 
-func msanread(addr unsafe.Pointer, sz uintptr)   { throw("race") }
-func msanwrite(addr unsafe.Pointer, sz uintptr)  { throw("race") }
+func msanread(addr unsafe.Pointer, sz uintptr)   { throw("msan") }
+func msanwrite(addr unsafe.Pointer, sz uintptr)  { throw("msan") }
 func msanmalloc(addr unsafe.Pointer, sz uintptr) { throw("msan") }
 func msanfree(addr unsafe.Pointer, sz uintptr)   { throw("msan") }