Fix Outdated Comment And Clean Up Grammar

days -> seconds and "in until to" -> "from"

Co-authored-by: Cy Rossignol <cy@rossignols.me>

src/neuralnet/accrual/snapshot.h

@@ -195,7 +195,7 @@ class SnapshotCalculator
     //! \brief Calculate the age of the active superblock to determine the
     //! duration of the accrual period.
     //!
-    //! \return Superblock age as days in until to the payment time.
+    //! \return Superblock age as seconds from the payment time.
     //!
     int64_t SuperblockAge() const
     {