Fix support for bumps on golang.org/x/crypto/x509roots/fallback

[pjbgf]

For multi-module repositories, Renovate is not using the mod specific version, instead it is using the repository level tag.

Examples:

• chore(deps): update module golang.org/x/crypto/x509roots/fallback to v0.19.0 cis-operator#270
• chore(deps): update module golang.org/x/crypto/x509roots/fallback to v0.18.0 cis-operator#251
• chore(deps): update module golang.org/x/crypto/x509roots/fallback to v0.17.0 cis-operator#237

[pjbgf]

This sub-module is not tagged as a release by itself, and Renovate does not seem to manage this well.

I have created a discussion upstream to confirm whether there is a good solution for this.

In the mean time, I am adding this to the ignored list so that it stops creating failing PRs.