all: update go.mod

[eliben]

Following the fix of #1958, we can remove the vault requirement in go.mod. For this PR:

• Removed vault from go.mod
• Reran go test ./..., and the go tool updated go.mod

[codecov]

Codecov Report

Merging #2027 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2027      +/-   ##
==========================================
- Coverage   77.54%   77.52%   -0.03%     
==========================================
  Files          82       82              
  Lines        9671     9671              
==========================================
- Hits         7499     7497       -2     
- Misses       1630     1632       +2     
  Partials      542      542

Impacted Files	Coverage Δ
pubsub/kafkapubsub/kafka.go	83.45% <0%> (-0.74%)	⬇️

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[vangent]

Tests failed:

FAIL: dependencies changed; run: internal/testing/listdeps.sh > internal/testing/alldeps

[eliben]

Tests failed:

FAIL: dependencies changed; run: internal/testing/listdeps.sh > internal/testing/alldeps

Yes, rerunning tests now. vault masked a bunch of packages it seems, so now they explicitly appear in go list, not sure why... but they all are used by vault/api. Maybe a general refactoring of their packages