Fix version in DeePMDConfigVersion.cmake (#4577)

The double quotes end up as follows in `DeePMDConfigVersion.cmake`:
```cmake
set(PACKAGE_VERSION "$<IF:?:"0.0.0">")
```
This result in the following warning:
```
CMake Error (dev) at /opt/cp2k-toolchain/install/deepmd-kit-3.0.1/lib/cmake/DeePMD/DeePMDConfigVersion.cmake:10:                                             
  Syntax Warning in cmake code at column 30                                                                                                                                                                                                                                                                                
  Argument not separated from preceding token by whitespace.                                                                                                 
Call Stack (most recent call first):                                                                                                                         
  CMakeLists.txt:703 (find_package)                                                                                                                          
This error is for project developers. Use -Wno-error=dev to suppress it.      
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Bug Fixes**
- Improved the project’s version handling to ensure that when no version
is provided, a reliable default is used, resulting in more consistent
and accurate version information for end-users.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: RMeli

source/CMakeLists.txt

@@ -580,7 +580,7 @@ if(BUILD_CPP_IF
   set(version_file "${generated_dir}/${CMAKE_PROJECT_NAME}ConfigVersion.cmake")
   write_basic_package_version_file(
     ${version_file}
-    VERSION $<IF:${GIT_SUMM}?${GIT_SUMM}:"0.0.0">
+    VERSION $<IF:${GIT_SUMM}?${GIT_SUMM}:0.0.0>
     COMPATIBILITY AnyNewerVersion)
   install(
     EXPORT ${targets_export_name}