Remove "are you sure?" from lint msg.

No added value, and leads to punctuation clash.

src/attrs.rs

@@ -99,7 +99,7 @@ fn check_attrs(cx: &LateContext, span: Span, name: &Name,
                 if always != &"always" { continue; }
                 span_lint(cx, INLINE_ALWAYS, attr.span, &format!(
                     "you have declared `#[inline(always)]` on `{}`. This \
-                     is usually a bad idea. Are you sure?",
+                     is usually a bad idea",
                     name));
             }
         }