[ROOT-10190] Excluded fastcloningeventtree test in roottest.git should be re-enabled back

[vepadulano]

Explain what you would like to see improved and how.

From https://its.cern.ch/jira/browse/ROOT-10190

Files for fastcloningeventtree were moved from filemerger directory during its migration to CMake. During migration to CMake, it was found that test was not running for some time and as a result it is not compiling.

Fastcloningeventtree is temporary disabled for this reason.

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