Fix deprecated dynamic exception in fboss/agent/hw/bcm/BcmError.h +5

Summary:
X-link: facebookresearch/fbpcf#539

LLVM has detected a violation of `-Wdeprecated-dynamic-exception-spec`. Dynamic exceptions were removed in C++17. This diff fixes the deprecated instance(s).

See [Dynamic exception specification](https://en.cppreference.com/w/cpp/language/except_spec) and [noexcept specifier](https://en.cppreference.com/w/cpp/language/noexcept_spec).

Reviewed By: palmje

Differential Revision: D57636124

fbshipit-source-id: 90ff1837d7d7aa919ea19d380b638a04b7d19adf

Author: r-barnes

folly/test/ExceptionWrapperTest.cpp

@@ -473,7 +473,7 @@ namespace {
 struct ThrownException {};
 struct InSituException : std::exception {
   InSituException() = default;
-  InSituException(const InSituException&) throw() {}
+  InSituException(const InSituException&) noexcept {}
 };
 struct OnHeapException : std::exception {
   OnHeapException() = default;