Bump distroless/base in /trillian/examples/deployment/docker/ctfe (#1188

)

Bumps distroless/base from `a35b652` to `b31a6e0`.

---
updated-dependencies:
- dependency-name: distroless/base
  dependency-type: direct:production
...

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

trillian/examples/deployment/docker/ctfe/Dockerfile

@@ -12,7 +12,7 @@ COPY . .
 
 RUN CGO_ENABLED=0 go build ./trillian/ctfe/ct_server
 
-FROM gcr.io/distroless/base@sha256:a35b6525fde5572656e24109064dd147fbaedc26e5a7ccd147ff3ed3a4308c21
+FROM gcr.io/distroless/base@sha256:b31a6e02605827e77b7ebb82a0ac9669ec51091edd62c2c076175e05556f4ab9
 
 COPY --from=build /build/ct_server /