DebugInfo: remove unnecessary mtriple from test/DebugInfo/X86/abstract_origin.ll

The test already specifies a triple in the IR itself.

Based on post-commit feedback from Luís Marques.
diff --git a/llvm/test/DebugInfo/X86/abstract_origin.ll b/llvm/test/DebugInfo/X86/abstract_origin.ll
index 4cf4905..a9eb970 100644
--- a/llvm/test/DebugInfo/X86/abstract_origin.ll
+++ b/llvm/test/DebugInfo/X86/abstract_origin.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=x86_64 -filetype=obj %s -o - | llvm-dwarfdump -debug-info - | FileCheck %s
+; RUN: llc -filetype=obj %s -o - | llvm-dwarfdump -debug-info - | FileCheck %s
 ; Generated at -O2 from:
 ;   void f();
 ;   __attribute__((always_inline)) void g() {