Follow-up to [68db1ff9c44fa9c3]: The number of registers needed by

Follow-up to [68db1ff9c44fa9c3]:  The number of registers needed by
PRAGMA foreign_key_check was increased too late for an assert() deep
down inside of sqlite3ExprCode().  So move the size increase a little
earlier.
[forum:/forumpost/79c9e4797d|Forum post 79c9e4797d].

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