Cocoa: Remove checks for pre-10.8 SDK

OS X 10.8 is now the minimum required version but these checks were not
removed when that change was made.

src/cocoa_init.m

@@ -435,13 +435,9 @@ static GLFWbool initializeTIS(void)
 
         if ([[NSBundle mainBundle] pathForResource:@"MainMenu" ofType:@"nib"])
         {
-#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1080
             [[NSBundle mainBundle] loadNibNamed:@"MainMenu"
                                           owner:NSApp
                                 topLevelObjects:&_glfw.ns.nibObjects];
-#else
-            [[NSBundle mainBundle] loadNibNamed:@"MainMenu" owner:NSApp];
-#endif
         }
         else
             createMenuBar();

src/nsgl_context.m

@@ -232,9 +232,7 @@ GLFWbool _glfwCreateContextNSGL(_GLFWwindow* window,
         //       Info.plist for unbundled applications
         // HACK: This assumes that NSOpenGLPixelFormat will remain
         //       a straightforward wrapper of its CGL counterpart
-#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1080
         addAttrib(kCGLPFASupportsAutomaticGraphicsSwitching);
-#endif /*MAC_OS_X_VERSION_MAX_ALLOWED*/
     }
 
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= 101000