main : update log text (EOS to EOG) (#7104)

* Update log text (EOS to EOG)

The log text "found EOS" is no longer always correct, here, because there is now an is-EOG check that also returns true for EOT.

* Improve log msg. further by using "an" instead of "some".

As suggested, to avoid misunderstanding (no multiple EOG tokens found, just one).