Remove test case, ValueFlow will truncate and sign-extend values

test/testcharvar.cpp

@@ -81,14 +81,6 @@ private:
               "}");
         ASSERT_EQUALS("", errout.str());
 
-        check("int buf[256];\n"
-              "void foo()\n"
-              "{\n"
-              "    signed char ch = 0x80;\n"
-              "    buf[ch] = 0;\n"
-              "}");
-        ASSERT_EQUALS("[test.cpp:5]: (warning) Signed 'char' type used as array index.\n", errout.str());
-
         check("int buf[256];\n"
               "void foo()\n"
               "{\n"