Remove superfluous C++ linkage specification from cassert header

Author: lbushi25

sycl/test/basic_tests/assert_header_with_c_linkage.cpp

@@ -1,18 +1,13 @@
-// RUN: %clangxx -fsycl -DASSERT -fsyntax-only %s
-// RUN: %clangxx -fsycl -DCASSERT -fsyntax-only %s
+// RUN: %clangxx -fsycl -fsyntax-only %s
 
-// Verify that compilation works when assert.h/cassert is wrapped by a C linkage
+// Verify that compilation works when assert.h is wrapped by a C linkage
 // specification.
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#if defined(ASSERT)
 #include <assert.h>
-#elif defined(CASSERT)
-#include <cassert>
-#endif
 
 #ifdef __cplusplus
 }