[Build-deps]: Bump contrib.go.opencensus.io/exporter/prometheus (#2021)

Bumps [contrib.go.opencensus.io/exporter/prometheus](https://github.com/census-ecosystem/opencensus-go-exporter-prometheus) from 0.3.0 to 0.4.0.
- [Release notes](https://github.com/census-ecosystem/opencensus-go-exporter-prometheus/releases)
- [Commits](census-ecosystem/opencensus-go-exporter-prometheus@v0.3.0...v0.4.0)

---
updated-dependencies:
- dependency-name: contrib.go.opencensus.io/exporter/prometheus
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

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

go.mod

@@ -2,8 +2,7 @@ module github.com/cs3org/reva
 
 require (
 	bou.ke/monkey v1.0.2
-	contrib.go.opencensus.io/exporter/jaeger v0.2.1
-	contrib.go.opencensus.io/exporter/prometheus v0.3.0
+	contrib.go.opencensus.io/exporter/prometheus v0.4.0
 	github.com/BurntSushi/toml v0.4.1
 	github.com/Masterminds/goutils v1.1.0 // indirect
 	github.com/Masterminds/semver v1.5.0 // indirect
@@ -25,7 +24,6 @@ require (
 	github.com/go-openapi/strfmt v0.19.5 // indirect
 	github.com/go-sql-driver/mysql v1.6.0
 	github.com/golang-jwt/jwt v3.2.2+incompatible
-	github.com/golang/mock v1.4.4 // indirect
 	github.com/golang/protobuf v1.5.2
 	github.com/gomodule/redigo v1.8.5
 	github.com/google/go-cmp v0.5.6
@@ -41,6 +39,7 @@ require (
 	github.com/mattn/go-sqlite3 v1.14.8
 	github.com/minio/minio-go/v7 v7.0.12
 	github.com/mitchellh/copystructure v1.0.0 // indirect
+	github.com/mitchellh/go-testing-interface v1.0.0 // indirect
 	github.com/mitchellh/mapstructure v1.4.1
 	github.com/onsi/ginkgo v1.16.4
 	github.com/onsi/gomega v1.15.0
@@ -61,14 +60,12 @@ require (
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.22.0
 	go.opentelemetry.io/otel v1.0.0-RC2
 	go.opentelemetry.io/otel/exporters/jaeger v1.0.0-RC2
-	go.opentelemetry.io/otel/metric v0.20.0 // indirect
 	go.opentelemetry.io/otel/sdk v1.0.0-RC2
 	go.opentelemetry.io/otel/trace v1.0.0-RC2
 	golang.org/x/crypto v0.0.0-20201216223049-8b5274cf687f
-	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d
-	golang.org/x/sys v0.0.0-20210423185535-09eb48e85fd7
+	golang.org/x/oauth2 v0.0.0-20210514164344-f6687ab2804c
+	golang.org/x/sys v0.0.0-20210603081109-ebe580a85c40
 	golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1
-	google.golang.org/genproto v0.0.0-20200806141610-86f49bd18e98 // indirect
 	google.golang.org/grpc v1.39.1
 	google.golang.org/protobuf v1.27.1
 	gopkg.in/square/go-jose.v2 v2.5.1 // indirect