Bump golang from 1.21-alpine to 1.22-alpine in /example/zipkin

Bumps golang from 1.21-alpine to 1.22-alpine.

---
updated-dependencies:
- dependency-name: golang
  dependency-type: direct:production
...

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

example/zipkin/Dockerfile

@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-FROM golang:1.21-alpine
+FROM golang:1.22-alpine
 COPY . /go/src/github.com/open-telemetry/opentelemetry-go/
 WORKDIR /go/src/github.com/open-telemetry/opentelemetry-go/example/zipkin/
 RUN go install ./main.go