spirv: update failing / passing tests

Some tests are now failing due to debug info changes, some tests
now pass due to improved compiler functionality.

test/behavior/usingnamespace.zig

@@ -55,7 +55,6 @@ usingnamespace @import("usingnamespace/a.zig");
 test "two files usingnamespace import each other" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
-    if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
 
     try expect(@This().ok());
 }