Fix test failure with micromamba

The following discussion from !148 (merged) should be addressed:

• @lmoureau started a discussion:

  There is an issue with the tests when the dictionary is not in $LD_LIBRARY_PATH. This is the case in the build directory, where the libraries is loaded via RPATH. Not sure why it works in the CI; it doesn't on my laptop (ROOT 6.30/04).

ROOT regression?