chore: bump Go version to 1.26.5

[rohanKanojia]

What does this PR do?

Update go.mod, CI workflow, and controller Dockerfile to use ubi9/go-toolset 1.26.5-1784190466.

Assisted-by: opencode

What issues does this PR fix or reference?

Is it tested? How?

[openshift-ci]

Hi @rohanKanojia. Thanks for your PR.

I'm waiting for a redhat-developer member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

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