Switch dependency from boltdb to bbolt

[amasover]

Switching to bbolt for security/stability reasons.

I did my best to update go.mod, go.sum and the vendored dependencies without touching anything else.

Fixes: #974

[codecov]

Codecov Report

Merging #980 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #980   +/-   ##
=======================================
  Coverage   72.12%   72.12%           
=======================================
  Files          65       65           
  Lines        5316     5316           
=======================================
  Hits         3834     3834           
  Misses       1186     1186           
  Partials      296      296           

Impacted Files	Coverage Δ
server/events/db/boltdb.go	74.28% <ø> (ø)

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