It's not really necessary if the information about if the lambda was a
trailing lambda can be directly saved in FirAnonymousFunctionExpression.
Removing the FIR node uncovered a couple of bugs
(UNINITIALIZED_ENUM_ENTRY, ERROR_IN_CONTRACT_DESCRIPTION) that were
caused by assuming that a lambda is always a trailing lambda.
#KT-66124
This change is required to properly support such declarations in lazy
resolution mode as we usually replaced initializers with lazy
expressions during the body calculation phase
^KT-62840
Kirill Rakhman