[gdb/testsuite] Fix gdb.cp/m-static.exp on arm

With test-case gdb.cp/m-static.exp on arm-linux, I get:
...
(gdb) ptype test5.single_constructor^M
type = class single_constructor {^M
^M
  public:^M
    single_constructor(void);^M
    ~single_constructor(void);^M
} *(single_constructor * const)^M
(gdb) FAIL: gdb.cp/m-static.exp: simple object instance, ptype constructor
...

The test-case expects:
- no empty line before "public:", and
- no "~single_constructor(void)", but "~single_constructor()"

The latter is due to commit 137c886e ("[gdb/c++] Print destructor the same
for gcc and clang").

The failing test is in a part only enabled for is_aarch32_target == 1, so it
looks like it was left behind.

I'm assuming the same happened for the other difference.

Fix this by updating the regexps to match the observed output.

Tested on arm-linux.

Approved-By: Andrew Burgess <aburgess@redhat.com>