[BE] Add missing override to remove build warning spam (#107191)
```
In file included from /local/pytorch3/test/cpp/api/optim.cpp:7:
local/pytorch3/test/cpp/api/support.h:44:3: warning: '~WarningCapture' overrides a destructor but is not marked 'override' [-Winconsistent-missing-destructor-override]
~WarningCapture() {
^
local/pytorch3/c10/util/Exception.h:167:11: note: overridden virtual function is here
virtual ~WarningHandler() = default;
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107191
Approved by: https://github.com/janeyx99
