wasm-linker: Fix memory leak

This fixes a memory leak when an object file contains one or more element sections which
then contains one or more function indexes. This commit ensures the slice of index functions
for each element section will be freed upon resource deallocation also.

src/link/Wasm/Object.zig

@@ -133,6 +133,9 @@ pub fn deinit(self: *Object, gpa: Allocator) void {
     gpa.free(self.memories);
     gpa.free(self.globals);
     gpa.free(self.exports);
+    for (self.elements) |el| {
+        gpa.free(el.func_indexes);
+    }
     gpa.free(self.elements);
     gpa.free(self.features);
     for (self.relocations.values()) |val| {