Do not stop obsolete mr closing and vulnerability issue creation when open mr limit reached

Fixes a bug where app wouldn't not create vulnerability issue in case update mr was not created due to open mr limit reached.

Related to: https://gitlab.com/dependabot-gitlab/dependabot/-/issues/257

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Allure report

allure-report-publisher generated test report!

rspec: ✅ test report for 9ef60a09

+------------------------------------------------------------------+
|                        behaviors summary                         |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| controllers | 25     | 0      | 0       | 0     | 25    | ✅     |
| services    | 174    | 0      | 0       | 0     | 174   | ✅     |
| jobs        | 14     | 0      | 0       | 0     | 14    | ✅     |
| tasks       | 9      | 0      | 0       | 0     | 9     | ✅     |
| models      | 4      | 0      | 0       | 0     | 4     | ✅     |
| system      | 10     | 0      | 0       | 0     | 10    | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 236    | 0      | 0       | 0     | 236   | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+