don't use type annotations as they aren't supported on julia 1.6

These were not the high-impact part of the previous commit.

src/GLib/signals.jl

@@ -288,7 +288,7 @@ function new_gsource(source_funcs::_GSourceFuncs)
     gsource
 end
 
-expiration::UInt64 = UInt64(0)
+expiration = UInt64(0)
 _isempty_workqueue() = isempty(Base.Workqueue)
 uv_loop_alive(evt) = ccall(:uv_loop_alive, Cint, (Ptr{Nothing},), evt) != 0
 
@@ -341,8 +341,7 @@ function uv_dispatch(src::Ptr{Nothing}, callback::Ptr{Nothing}, data)
     return ccall(callback, Cint, (UInt,), data)
 end
 
-sizeof_gclosure::Int = 0
-jlref_quark::UInt32 = 0
+sizeof_gclosure = 0
 function __init__gtype__()
     global jlref_quark = quark"julia_ref"
     global sizeof_gclosure = Sys.WORD_SIZE