Fix compile warning from CUDF_FUNC_RANGE in a member function (#11798)

Compile warning was introduced in #11652 in `bgzip_data_chunk_source.cu`. The warning can be seen here https://gpuci.gpuopenanalytics.com/job/rapidsai/job/gpuci/job/cudf/job/prb/job/cudf-cpu-cuda-build/CUDA=11.5/12417/consoleFull (search for `177-D`)
```
/cudf/cpp/src/io/text/bgzip_data_chunk_source.cu(362): warning #177-D: variable "nvtx3_range__" was declared but never referenced
```
The `nvtx3_range__` is part of the `CUDF_FUNC_RANGE()` macro. The warning is incorrect and likely a compiler bug. The workaround in this PR is to add `[[maybe_unused]]` to the variable declaration.

I was not able to create a small reproducer for compile bug filing.

Authors:
  - David Wendt (https://github.com/davidwendt)

Approvers:
  - Tobias Ribizel (https://github.com/upsj)
  - MithunR (https://github.com/mythrocks)

URL: #11798

cpp/include/cudf/detail/nvtx/nvtx3.hpp

@@ -1907,7 +1907,7 @@ inline void mark(event_attributes const& attr) noexcept
 #define NVTX3_FUNC_RANGE_IN(D)                                                 \
   static ::nvtx3::registered_message<D> const nvtx3_func_name__{__func__};     \
   static ::nvtx3::event_attributes const nvtx3_func_attr__{nvtx3_func_name__}; \
-  ::nvtx3::domain_thread_range<D> const nvtx3_range__{nvtx3_func_attr__};
+  [[maybe_unused]] ::nvtx3::domain_thread_range<D> const nvtx3_range__{nvtx3_func_attr__};
 
 /**
  * @brief Convenience macro for generating a range in the global domain from the