`CUDAAgent.CUDARTCFuncMapPair` unused

CUDAAgent includes a typedef 

```
typedef std::pair<const std::string, std::unique_ptr<jitify2::KernelData>> CUDARTCFuncMapPair;
```

This appears to be unused, so can probably be removed.

Based on the docstring, it (probably?) was the value type of 

```
typedef std::map<const std::string, std::unique_ptr<jitify2::KernelData>> CUDARTCFuncMap;
```

but that is not currently the case