[3.14] gh-128605: Revert "Add branch protections for x86_64 in asm_tr…ampoline.S (GH-128606) (GH-135077)" (GH-135175)

This reverts commit 899cca6,
which broke buildbots.
(cherry picked from commit b477e21)

Co-authored-by: Petr Viktorin <encukou@gmail.com>

Author: encukou

Python/asm_trampoline.S

@@ -9,9 +9,6 @@
 # }
 _Py_trampoline_func_start:
 #ifdef __x86_64__
-#if defined(__CET__) && (__CET__ & 1)
-    endbr64
-#endif
     sub    $8, %rsp
     call    *%rcx
     add    $8, %rsp
@@ -37,22 +34,3 @@ _Py_trampoline_func_start:
     .globl	_Py_trampoline_func_end
 _Py_trampoline_func_end:
     .section        .note.GNU-stack,"",@progbits
-# Note for indicating the assembly code supports CET
-#if defined(__x86_64__) && defined(__CET__) && (__CET__ & 1)
-    .section    .note.gnu.property,"a"
-    .align 8
-    .long    1f - 0f
-    .long    4f - 1f
-    .long    5
-0:
-    .string  "GNU"
-1:
-    .align 8
-    .long    0xc0000002
-    .long    3f - 2f
-2:
-    .long    0x3
-3:
-    .align 8
-4:
-#endif // __x86_64__

Python/perf_jit_trampoline.c

@@ -472,11 +472,6 @@ elf_init_ehframe(ELFObjectContext* ctx)
                  DWRF_U8(0); /* Augmentation data. */
     /* Registers saved in CFRAME. */
 #ifdef __x86_64__
-#  if defined(__CET__) && (__CET__ & 1)
-                 DWRF_U8(DWRF_CFA_advance_loc | 8);
-#  else
-                 DWRF_U8(DWRF_CFA_advance_loc | 4);
-#  endif
                  DWRF_U8(DWRF_CFA_advance_loc | 4);
                  DWRF_U8(DWRF_CFA_def_cfa_offset); DWRF_UV(16);
                  DWRF_U8(DWRF_CFA_advance_loc | 6);