Fix wrong casing in paths

Author: chengluyu

hkmc2/shared/src/test/mlscript/ucs/normalization/UnifyTupleElements.mls

@@ -1,10 +1,10 @@
 :js
 :ucs desugared normalized
 
-:import ../Prelude/Option.mls
+:import ../prelude/Option.mls
 //│ Imported 3 member(s)
 
-:import ../Prelude/Tuple.mls
+:import ../prelude/Tuple.mls
 //│ Imported 2 member(s)
 
 // Normalization should unify fixed-length tuple patterns.

hkmc2/shared/src/test/mlscript/ucs/patterns/RestTuple.mls

@@ -1,7 +1,7 @@
 :js
 :ucs desugared
 
-:import ../Prelude/Tuple.mls
+:import ../prelude/Tuple.mls
 //│ Imported 2 member(s)
 
 // Drop the first and last elements.

hkmc2/shared/src/test/mlscript/ucs/patterns/SimpleTuple.mls

@@ -153,7 +153,7 @@ match_against_different_length([9, 11])
 match_against_different_length([13, 13, 13])
 //│ = 42
 
-:import ../Prelude/Option.mls
+:import ../prelude/Option.mls
 //│ Imported 3 member(s)
 
 :ucs desugared normalized