Fix narrowing in Cov3f

[jmcarcell]

BEGINRELEASENOTES

• Fix narrowing in Cov3f from int to float. This triggers a warning in GCC 13 and a compiler error in Clang 17.
• Fix a compiler error and a warning with Clang. The first one about constness of the LCIO pid handler and the other one about a lambda parameter not being used

ENDRELEASENOTES

The narrowing could be fixed in EDM4hep by doing static_cast<float> first but then there is no info when there is a narrowing conversion and there is possibly loss of some information because the destination type (float for CovNf) can't represent all the values of the original type. What I don't like is that it's a bit inconsistent in GCC (warning) and Clang (error).

The LCIO PID handler one is:

   80 |     for (const auto id : pidHandler.getAlgorithmIDs()) {
      |                          ^~~~~~~~~~
/LCIO/src/cpp/include/UTIL/PIDHandler.h:104:26: note: 'getAlgorithmIDs' declared here
  104 |     const EVENT::IntVec& getAlgorithmIDs() ;

[tmadlener]

Is this something compilers start to warn about?