Exercise: Profiles and cross-compiling fails due to different compiler version

The `arm-linux-gnueabihf-gcc` version included in Docker image is 9.4.0 and that causes the exercise to fail.
Changing `compiler.version=9` in `rpi_armv7` fixes the failure

```
-- Conan: Compiler GCC>=5, checking major version 7
-- Conan: Checking correct version: 9
CMake Error at ../conanbuildinfo.cmake:402 (message):
Detected a mismatch for the compiler version between your conan profile
settings and CMake:

Compiler version specified in your conan profile: 7

Compiler version detected in CMake: 9.4

Please check your conan profile settings (conan profile show
[default|your_profile_name])

P.S. You may set CONAN_DISABLE_CHECK_COMPILER CMake variable in order to
disable this check.
```

Start with the rpi_armv7 Conan profile and the Docker image configuration mentioned in the issue; compare the configured compiler.version with the arm-linux-gnueabihf-gcc version in the image. Update the mismatched setting and verify that the exercise no longer reports a compiler-version mismatch during cross-compilation.

Written by the indexing model from the issue text.