drop unused nostd includes flagged by include-what-you-use

Author: ayush-that

sdk/src/trace/samplers/probability.cc

@@ -9,7 +9,6 @@
 #include <string>
 
 #include "opentelemetry/nostd/function_ref.h"
-#include "opentelemetry/nostd/span.h"
 #include "opentelemetry/nostd/string_view.h"
 #include "opentelemetry/sdk/common/global_log_handler.h"
 #include "opentelemetry/sdk/trace/sampler.h"

sdk/test/trace/probability_sampler_test.cc

@@ -12,7 +12,6 @@
 
 #include "opentelemetry/common/key_value_iterable_view.h"
 #include "opentelemetry/nostd/span.h"
-#include "opentelemetry/nostd/string_view.h"
 #include "opentelemetry/nostd/utility.h"
 #include "opentelemetry/sdk/trace/sampler.h"
 #include "opentelemetry/sdk/trace/samplers/probability.h"