BUG#42415 UPDATE with LIMIT clause unsafe for statement format even when ORDER BY PK

Change the warning message to 'Statement may not be safe to log in
statement format' to indicate that the decision on whether a
statement is safe or not is heuristic, and we are conservative.

sql/share/errmsg.txt

@@ -6076,7 +6076,7 @@ ER_SLAVE_INCIDENT
 ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENT
         eng "Table has no partition for some existing values"
 ER_BINLOG_UNSAFE_STATEMENT
-        eng "Statement is not safe to log in statement format."
+        eng "Statement may not be safe to log in statement format."
         swe "Detta r inte skert att logga i statement-format."
 ER_SLAVE_FATAL_ERROR
         eng "Fatal error: %s"