Fix parsing foreign key constraints

[k1LoW]

Fix #476

[github-actions]

Code Metrics Report

	main (0dddf16)	#489 (be12ab3)	+/-
Coverage	64.5%	62.5%	-2.0%
Code to Test Ratio	1:0.4	1:0.4	+0.0
Test Execution Time	3m47s	5m3s	+1m16s

Details

  |                     | main (0dddf16) | #489 (be12ab3) |  +/-   |
  |---------------------|----------------|----------------|--------|
- | Coverage            |          64.5% |          62.5% |  -2.0% |
  |   Files             |             36 |             36 |      0 |
  |   Lines             |           3682 |           3690 |     +8 |
- |   Covered           |           2375 |           2307 |    -68 |
+ | Code to Test Ratio  |          1:0.4 |          1:0.4 |   +0.0 |
  |   Code              |           9587 |           9602 |    +15 |
+ |   Test              |           3880 |           3910 |    +30 |
- | Test Execution Time |          3m47s |           5m3s | +1m16s |

Code coverage of files in pull request scope (80.8% → 80.8%)

Files	Coverage	+/-
drivers/mysql/mysql.go	73.0%	+0.2%
drivers/postgres/postgres.go	81.2%	-0.1%
drivers/sqlite/sqlite.go	89.7%	+0.1%

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Reported by octocov