fix comment, seconds not sections (#210)

* fix comment, seconds not sections

* make the build go green
diff --git a/google/oauth2/service_account.py b/google/oauth2/service_account.py
index 81b5dab..54bd8d6 100644
--- a/google/oauth2/service_account.py
+++ b/google/oauth2/service_account.py
@@ -79,7 +79,7 @@
 from google.auth import jwt
 from google.oauth2 import _client
 
-_DEFAULT_TOKEN_LIFETIME_SECS = 3600  # 1 hour in sections
+_DEFAULT_TOKEN_LIFETIME_SECS = 3600  # 1 hour in seconds
 
 
 class Credentials(credentials.Signing,