[Geneva] Update opentelemetry to 1.21.0

Author: ThomsonTan

.github/workflows/fluentd.yml

@@ -29,7 +29,7 @@ jobs:
         uses: actions/checkout@v3
         with:
           repository: "open-telemetry/opentelemetry-cpp"
-          ref: "v1.19.0"
+          ref: "v1.21.0"
           path: "opentelemetry-cpp"
           submodules: "recursive"
       - name: setup dependencies

.github/workflows/geneva_metrics.yml

@@ -24,7 +24,7 @@ jobs:
         uses: actions/checkout@v3
         with:
           repository: "open-telemetry/opentelemetry-cpp"
-          ref: "v1.20.0"
+          ref: "v1.21.0"
           path: "otel_cpp"
           submodules: "recursive"
       - name: setup

.github/workflows/user_events.yml

@@ -27,7 +27,7 @@ jobs:
         uses: actions/checkout@v3
         with:
           repository: "open-telemetry/opentelemetry-cpp"
-          ref: "v1.20.0"
+          ref: "v1.21.0"
           path: "opentelemetry-cpp"
           submodules: "recursive"
       - name: setup dependencies