neg-multiply: make lint adhere to lint message convention

Author: matthiaskrgr

clippy_lints/src/neg_multiply.rs

@@ -47,7 +47,7 @@ fn check_mul(cx: &LateContext<'_>, span: Span, lit: &Expr<'_>, exp: &Expr<'_>) {
         if let Constant::Int(1) = consts::lit_to_constant(&l.node, cx.typeck_results().expr_ty_opt(lit));
         if cx.typeck_results().expr_ty(exp).is_integral();
         then {
-            span_lint(cx, NEG_MULTIPLY, span, "Negation by multiplying with `-1`");
+            span_lint(cx, NEG_MULTIPLY, span, "negation by multiplying with `-1`");
         }
     }
 }

tests/ui/neg_multiply.stderr

@@ -1,12 +1,12 @@
-error: Negation by multiplying with `-1`
+error: negation by multiplying with `-1`
   --> $DIR/neg_multiply.rs:27:5
    |
 LL |     x * -1;
    |     ^^^^^^
    |
    = note: `-D clippy::neg-multiply` implied by `-D warnings`
 
-error: Negation by multiplying with `-1`
+error: negation by multiplying with `-1`
   --> $DIR/neg_multiply.rs:29:5
    |
 LL |     -1 * x;