Bump bitbucket.org/creachadair/shell from 0.0.7 to 0.0.8 (#3266)

Bumps [bitbucket.org/creachadair/shell](https://bitbucket.org/creachadair/shell) from 0.0.7 to 0.0.8.
- [Commits](https://bitbucket.org/creachadair/shell/branches/compare/v0.0.8..v0.0.7)

---
updated-dependencies:
- dependency-name: bitbucket.org/creachadair/shell
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -3,7 +3,7 @@ module github.com/google/trillian
 go 1.20
 
 require (
-	bitbucket.org/creachadair/shell v0.0.7
+	bitbucket.org/creachadair/shell v0.0.8
 	cloud.google.com/go/spanner v1.53.1
 	contrib.go.opencensus.io/exporter/stackdriver v0.13.14
 	github.com/apache/beam/sdks/v2 v2.52.0

go.sum

@@ -1,5 +1,5 @@
-bitbucket.org/creachadair/shell v0.0.7 h1:Z96pB6DkSb7F3Y3BBnJeOZH2gazyMTWlvecSD4vDqfk=
-bitbucket.org/creachadair/shell v0.0.7/go.mod h1:oqtXSSvSYr4624lnnabXHaBsYW6RD80caLi2b3hJk0U=
+bitbucket.org/creachadair/shell v0.0.8 h1:3yM6JcAfaGWzjzcCamTblzSIWXm/YSs0PFGIzBm2HTo=
+bitbucket.org/creachadair/shell v0.0.8/go.mod h1:vINzudofoUXZSJ5tREgpy+Etyjsag3ait5WOWImEVZ0=
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 cloud.google.com/go v0.34.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 cloud.google.com/go v0.38.0/go.mod h1:990N+gfupTy94rShfmMCWGDn0LpTmnzTp2qbd1dvSRU=