oauth2: fix some typos in code comments

Change-Id: I3bd85f097e30d693965541eac65df057288c2086
Reviewed-on: https://go-review.googlesource.com/73130
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/internal/token.go b/internal/token.go
index cf959ea..0460957 100644
--- a/internal/token.go
+++ b/internal/token.go
@@ -20,7 +20,7 @@
 	"golang.org/x/net/context/ctxhttp"
 )
 
-// Token represents the crendentials used to authorize
+// Token represents the credentials used to authorize
 // the requests to access protected resources on the OAuth 2.0
 // provider's backend.
 //
diff --git a/token.go b/token.go
index 7a3167f..bdac1de 100644
--- a/token.go
+++ b/token.go
@@ -20,7 +20,7 @@
 // expirations due to client-server time mismatches.
 const expiryDelta = 10 * time.Second
 
-// Token represents the crendentials used to authorize
+// Token represents the credentials used to authorize
 // the requests to access protected resources on the OAuth 2.0
 // provider's backend.
 //