test: remove some tests that are now covered well enough by test-stack-traces

The amount of cross compilation required for these tests was too time-consuming
for how much value they added. test-stack-traces now cover these well enough,
especially as we add more exotic machines to the CI fleet to run native tests.

Author: alexrp

test/cases/pic_freestanding.zig

@@ -193,9 +193,6 @@
         .empty_global_error_set = .{
             .path = "empty_global_error_set",
         },
-        .omit_cfi = .{
-            .path = "omit_cfi",
-        },
         .config_header = .{
             .path = "config_header",
         },