Bump go.opentelemetry.io/otel/exporters/otlp in /examples/demo/app

Bumps [go.opentelemetry.io/otel/exporters/otlp](https://github.com/open-telemetry/opentelemetry-go) from 0.14.0 to 0.15.0.
- [Release notes](https://github.com/open-telemetry/opentelemetry-go/releases)
- [Changelog](https://github.com/open-telemetry/opentelemetry-go/blob/master/CHANGELOG.md)
- [Commits](open-telemetry/opentelemetry-go@v0.14.0...v0.15.0)

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

examples/demo/app/go.mod

@@ -7,7 +7,7 @@ require (
  github.com/golang/protobuf v1.4.3 // indirect
  github.com/kr/pretty v0.1.0 // indirect
  go.opentelemetry.io/otel v0.15.0
- go.opentelemetry.io/otel/exporters/otlp v0.14.0
+ go.opentelemetry.io/otel/exporters/otlp v0.15.0
  go.opentelemetry.io/otel/sdk v0.15.0
  golang.org/x/net v0.0.0-20200625001655-4c5254603344 // indirect
  golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211 // indirect

examples/demo/app/go.sum

@@ -37,8 +37,6 @@ github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMyw
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-github.com/google/go-cmp v0.5.3 h1:x95R7cp+rSeeqAMI2knLtQ0DKlaBhv2NrtrOvafPHRo=
-github.com/google/go-cmp v0.5.3/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.4 h1:L8R9j+yAqZuZjsqh/z+F1NCffTKKLShY6zXTItVIZ8M=
 github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/gofuzz v1.1.0 h1:Hsa8mG0dQ46ij8Sl2AYJDUv1oA9/d6Vk+3LG99Oe02g=
@@ -58,14 +56,10 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
 github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-go.opentelemetry.io/otel v0.14.0 h1:YFBEfjCk9MTjaytCNSUkp9Q8lF7QJezA06T71FbQxLQ=
-go.opentelemetry.io/otel v0.14.0/go.mod h1:vH5xEuwy7Rts0GNtsCW3HYQoZDY+OmBJ6t1bFGGlxgw=
 go.opentelemetry.io/otel v0.15.0 h1:CZFy2lPhxd4HlhZnYK8gRyDotksO3Ip9rBweY1vVYJw=
 go.opentelemetry.io/otel v0.15.0/go.mod h1:e4GKElweB8W2gWUqbghw0B8t5MCTccc9212eNHnOHwA=
-go.opentelemetry.io/otel/exporters/otlp v0.14.0 h1:B5uCGwaThlJMVpCeOxRkiVeOhT2t0GcZp8G+x219W5k=
-go.opentelemetry.io/otel/exporters/otlp v0.14.0/go.mod h1:DmFebmd697PT2nIQ6t6p1tx9KQFu+R2PGd+3W62OkAE=
-go.opentelemetry.io/otel/sdk v0.14.0 h1:Pqgd85y5XhyvHQlOxkKW+FD4DAX7AoeaNIDKC2VhfHQ=
-go.opentelemetry.io/otel/sdk v0.14.0/go.mod h1:kGO5pEMSNqSJppHAm8b73zztLxB5fgDQnD56/dl5xqE=
+go.opentelemetry.io/otel/exporters/otlp v0.15.0 h1:nZcr3JMl+ai/S3KbWash8g2SM3hW8CmntDjOeQS3cDs=
+go.opentelemetry.io/otel/exporters/otlp v0.15.0/go.mod h1:g51QPk9HYnS7LHT3ugk54ZCYH9EgZ8PutmpRPV9DOc4=
 go.opentelemetry.io/otel/sdk v0.15.0 h1:Hf2dl1Ad9Hn03qjcAuAq51GP5Pv1SV5puIkS2nRhdd8=
 go.opentelemetry.io/otel/sdk v0.15.0/go.mod h1:Qudkwgq81OcA9GYVlbyZ62wkLieeS1eWxIL0ufxgwoc=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=