renovate: ignore non-security npm updates

[palango]

Those updates take a lot of time of time to merge and provide little actual benefit. So lets disable non-security updates.

[github-actions[bot]]

Test failures:
TestUpdatedKeyfileContents: keystore account_cache_test.go:393: Emptying account file failed account_cache_test.go:394: wasn't notified of new accounts
This test report was produced by the test-summary action.  Made with ❤️ in Cambridge.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (0a9662f) 55.09% compared to head (05d3552) 55.07%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2248 +/- ## ========================================== - Coverage 55.09% 55.07% -0.02% ========================================== Files 684 684 Lines 114596 114596 ========================================== - Hits 63136 63117 -19 - Misses 47560 47586 +26 + Partials 3900 3893 -7 ```

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[github-actions[bot]]

Coverage from tests in ./e2e_test/... for ./consensus/istanbul/... at commit f0adb14e48288ff6d6e4d9320d5980afd4d17c2d

coverage: 51.1% of statements across all listed packages

coverage:  63.2% of statements in consensus/istanbul
coverage:  42.9% of statements in consensus/istanbul/announce
coverage:  55.9% of statements in consensus/istanbul/backend
coverage:   0.0% of statements in consensus/istanbul/backend/backendtest
coverage:  24.3% of statements in consensus/istanbul/backend/internal/replica
coverage:  66.1% of statements in consensus/istanbul/core
coverage:  50.0% of statements in consensus/istanbul/db
coverage:   0.0% of statements in consensus/istanbul/proxy
coverage:  64.2% of statements in consensus/istanbul/uptime
coverage:  51.8% of statements in consensus/istanbul/validator
coverage:  79.2% of statements in consensus/istanbul/validator/random