Update assembly code assertions

Rust 1.56 will cause these tests to start failing, so we can
preemptively update them to make the upgrade smoother.

Author: shepmaster

tests/spec/features/compilation_targets_spec.rb

@@ -54,7 +54,7 @@
         # We demangle the symbols
         expect(page).to have_content 'playground::main:'
 
-        expect(page).to have_content 'movq %rdi, %rax'
+        expect(page).to have_content 'addq $40, %rsp'
       end
     end
   end
@@ -71,7 +71,7 @@
         # We demangle the symbols
         expect(page).to have_content 'playground::main:'
 
-        expect(page).to have_content 'mov rax, rdi'
+        expect(page).to have_content 'add rsp, 40'
       end
     end
   end