Fix variable assignment thinko in hba.c

The intention behind 1b73d0b was to limit the use of TokenizedAuthLine,
but I have fat-fingered one location in parse_hba_line() when creating
the HbaLine, where this should use the local variable and not the value
coming from TokenizedAuthLine.  This logic is the exactly the same, but
let's be clean about all that on consistency grounds.

Reported-by: Julien Rouhaud
Discussion: https://postgr.es/m/20221026032730.k3sib5krgm7l6njk@jrouhaud

Author: michaelpq

src/backend/libpq/hba.c

@@ -1079,7 +1079,7 @@ parse_hba_line(TokenizedAuthLine *tok_line, int elevel)
 	HbaLine    *parsedline;
 
 	parsedline = palloc0(sizeof(HbaLine));
-	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->sourcefile = pstrdup(file_name);
 	parsedline->linenumber = line_num;
 	parsedline->rawline = pstrdup(tok_line->raw_line);