Remove leading zeros in version_config.hpp

[hcho3]

Since we switched to CalVer, the version strings contain leading zeros, e.g. 21.08.00. This leads to the generated header version_config.hpp to contain

#define RMM_VERSION_MAJOR 21
#define RMM_VERSION_MINOR 08
#define RMM_VERSION_PATCH 00

in which 08 is an invalid octal literal. See the resulting CI failure at https://gpuci.gpuopenanalytics.com/job/rapidsai/job/conda/job/xgboost/job/xgboost-conda-build/229/CUDA=11.0,PYTHON=3.7/console. The generated header is used by XGBoost.

Fix: Remove the leading zeros in the C++ constants so that we'd get

```cpp
#define RMM_VERSION_MAJOR 21
#define RMM_VERSION_MINOR 8
#define RMM_VERSION_PATCH 0

[ajschmidt8]

@gpucibot merge