[memprof] Clean up IndexedMemProfReader (NFC) (#94710)

Parameter "Version" is confusing in deserializeV012 and deserializeV3
because we also have member variable "Version".  Fortunately,
parameter "Version" and member variable "Version" always have the same
value because IndexedMemProfReader::deserialize initializes the member
variable and passes it to deserializeV012 and deserializeV3.

This patch removes the parameter.