cleanup(bigtable): remove OpenCensus example (#5707)

Author: coryan

CHANGELOG.md

@@ -9,6 +9,13 @@
 
 ## v1.23.0 - TBD
 
+### Bigtable
+
+* Removed [OpenCensus](https://opencensus.io) example. OpenCensus has merged
+  with OpenTracing into [OpenTelemetry](https://opentelemetry.io). The C++
+  development seems to have stalled, and we not longer believe it will ever
+  be mature enough to recommend for the `google-cloud-cpp` libraries.
+
 ## v1.22.0 - 2021-01
 
 ### Bigtable

bazel/google_cloud_cpp_deps.bzl

@@ -93,17 +93,6 @@ def google_cloud_cpp_deps():
             sha256 = "512e5a674bf31f8b7928a64d8adf73ee67b8fe88339ad29adaa3b84dbaa570d8",
         )
 
-    # Load opencensus.
-    if "io_opencensus_cpp" not in native.existing_rules():
-        http_archive(
-            name = "io_opencensus_cpp",
-            urls = [
-                "https://github.com/census-instrumentation/opencensus-cpp/archive/c900c4d723ef596f357b0e695e68e2fa725eec90.tar.gz",
-            ],
-            strip_prefix = "opencensus-cpp-c900c4d723ef596f357b0e695e68e2fa725eec90",
-            sha256 = "040753b92d0ea57e2e9ffe7fc51f4c954cfb352204dc967c04ae6100842d6f45",
-        )
-
     # Load gRPC and its dependencies, using a similar pattern to this function.
     if "com_github_grpc_grpc" not in native.existing_rules():
         http_archive(

ci/kokoro/docker/build-in-docker-cmake.sh

@@ -149,7 +149,6 @@ if [[ "${CLANG_TIDY:-}" == "yes" && (\
     local -r file_regex="$1"
     shift
     grep -E "${file_regex}" <<<"${MODIFIED}" |
-      grep -v google/cloud/bigtable/examples/opencensus |
       grep -v generator/integration_tests/golden |
       xargs --verbose -d '\n' -r -n 1 -P "${NCPU}" clang-tidy \
         -p="${BINARY_DIR}" "$@"