.gitignore: add schema/aur-schema-sqlite.sql

The SQLite schema is generated automatically from the main schema and
used in the test suite.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

.gitignore

@@ -7,3 +7,4 @@ aur.git/
 __pycache__/
 *.py[cod]
 test/test-results/
+schema/aur-schema-sqlite.sql