Won't build < v7.2.0 with gleam_stdlib >= 0.50

[Jarod1980]

Won't build < v7.2.0 with gleam_stdlib >= 0.50 because of a change to the location of DecodeError and others. gleam_stdlib >= 0.50 moved things to the separate decode module and so gtempo won't build < v7.2.0 with gleam_stblib >= 0.50