Close unit's file handle after reading in the bytecode

A file is left open on Windows, so it prevents it from being worked on.

Fixes RT#131378: https://rt.perl.org/Ticket/Display.html?id=131378

src/core/CompUnit/PrecompilationRepository.pm

@@ -69,6 +69,7 @@ class CompUnit::PrecompilationRepository::Default does CompUnit::PrecompilationR
         if $*RAKUDO_MODULE_DEBUG -> $RMD { $RMD("Loading precompiled\n$unit") }
 #?if moar
         my $handle := CompUnit::Loader.load-precompilation-file($unit.bytecode-handle);
+        $unit.close;
 #?endif
 #?if !moar
         my $handle := CompUnit::Loader.load-precompilation($unit.bytecode);