Run Nick G's spellchecker github.com/client9/misspell, carefuly fix what it found (#4235)

src/os/filesystem.go

@@ -30,7 +30,7 @@ type Filesystem interface {
 	// OpenFile opens the named file.
 	OpenFile(name string, flag int, perm FileMode) (uintptr, error)
 
-	// Mkdir creates a new directoy with the specified permission (before
+	// Mkdir creates a new directory with the specified permission (before
 	// umask). Some filesystems may not support directories or permissions.
 	Mkdir(name string, perm FileMode) error
 

src/os/seek_unix_bad.go

@@ -11,7 +11,7 @@ import (
 // In particular, on i386 and arm, the function syscall.seek is missing, breaking syscall.Seek.
 // This in turn causes os.(*File).Seek, time, io/fs, and path/filepath to fail to link.
 //
-// To temporarly let all the above at least link, provide a stub for syscall.seek.
+// To temporarily let all the above at least link, provide a stub for syscall.seek.
 // This belongs in syscall, but on linux, we use upstream's syscall.
 // Remove once we support Go Assembly.
 // TODO: make this a non-stub, and thus fix the whole problem?