runtime: fix typo in comment for cpuinit

Change-Id: Ie19e0354f813b042c995c0221072568eaa473bea
Reviewed-on: https://go-review.googlesource.com/114995
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/proc.go

@@ -479,7 +479,7 @@ func internal_cpu_initialize(env string)
 //go:linkname internal_cpu_debugOptions internal/cpu.debugOptions
 var internal_cpu_debugOptions bool
 
-// cpuinit extracts the environment variable GODEBUGCPU from the enviroment on
+// cpuinit extracts the environment variable GODEBUGCPU from the environment on
 // Linux and Darwin if the GOEXPERIMENT debugcpu was set and calls internal/cpu.initialize.
 func cpuinit() {
 	const prefix = "GODEBUGCPU="