Deprecation warnings reported from metrics_foo_library example

[dbarker]

Describe your environment
Ubuntu 24.04, default gcc, main at 37a57da

Steps to reproduce
build the examples that use the metrics_foo_library

What is the expected behavior?
no deprecation warnings should be reported.

What is the actual behavior?
The following warnings from deprecated semantic conventions are reported.

In file included from /home/runner/work/opentelemetry-cpp/opentelemetry-cpp/examples/common/metrics_foo_library/foo_library.cc:27:
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/api/include/opentelemetry/semconv/system_metrics.h: In function ‘opentelemetry::v1::nostd::shared_ptr<opentelemetry::v1::metrics::ObservableInstrument> opentelemetry::v1::semconv::system::CreateAsyncInt64MetricSystemCpuFrequency(opentelemetry::v1::metrics::Meter*)’:
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/api/include/opentelemetry/semconv/system_metrics.h:57:44: warning: ‘opentelemetry::v1::semconv::system::kMetricSystemCpuFrequency’ is deprecated [-Wdeprecated-declarations]
   57 |   return meter->CreateInt64ObservableGauge(kMetricSystemCpuFrequency, descrMetricSystemCpuFrequency,
      |                                            ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/api/include/opentelemetry/semconv/system_metrics.h:31:55: note: declared here
   31 | OPENTELEMETRY_DEPRECATED static constexpr const char *kMetricSystemCpuFrequency =
      |                                                       ^~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/api/include/opentelemetry/semconv/system_metrics.h:57:71: warning: ‘opentelemetry::v1::semconv::system::descrMetricSystemCpuFrequency’ is deprecated [-Wdeprecated-declarations]
   57 |   return meter->CreateInt64ObservableGauge(kMetricSystemCpuFrequency, descrMetricSystemCpuFrequency,
      |                                                                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/api/include/opentelemetry/semconv/system_metrics.h:33:55: note: declared here
   33 | OPENTELEMETRY_DEPRECATED static constexpr const char *descrMetricSystemCpuFrequency =
      |                                                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/api/include/opentelemetry/semconv/system_metrics.h:58:44: warning: ‘opentelemetry::v1::semconv::system::unitMetricSystemCpuFrequency’ is deprecated [-Wdeprecated-declarations]
   58 |                                            unitMetricSystemCpuFrequency);
      |                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/api/include/opentelemetry/semconv/system_metrics.h:35:55: note: declared here
   35 | OPENTELEMETRY_DEPRECATED static constexpr const char *unitMetricSystemCpuFrequency = "{Hz}";

Additional context

The CreateAsyncInt64MetricSystemCpuFrequency method is not called by the example and the warning appears to come from simplying including the semconv/system_metrics.h header.

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