Update int_plus_one suggestion text

This is now in line with the recommendations from here:
https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.Diagnostic.html#method.span_suggestion

Author: phansch

clippy_lints/src/int_plus_one.rs

@@ -158,7 +158,7 @@ impl IntPlusOne {
             |db| {
                 db.span_suggestion(
                     block.span,
-                    "change `>= y + 1` to `> y` as shown",
+                    "change it to",
                     recommendation,
                     Applicability::MachineApplicable, // snippet
                 );

tests/ui/int_plus_one.stderr

@@ -2,43 +2,27 @@ error: Unnecessary `>= y + 1` or `x - 1 >=`
   --> $DIR/int_plus_one.rs:9:13
    |
 LL |     let _ = x >= y + 1;
-   |             ^^^^^^^^^^
+   |             ^^^^^^^^^^ help: change it to: `x > y`
    |
    = note: `-D clippy::int-plus-one` implied by `-D warnings`
-help: change `>= y + 1` to `> y` as shown
-   |
-LL |     let _ = x > y;
-   |             ^^^^^
 
 error: Unnecessary `>= y + 1` or `x - 1 >=`
   --> $DIR/int_plus_one.rs:10:13
    |
 LL |     let _ = y + 1 <= x;
-   |             ^^^^^^^^^^
-help: change `>= y + 1` to `> y` as shown
-   |
-LL |     let _ = y < x;
-   |             ^^^^^
+   |             ^^^^^^^^^^ help: change it to: `y < x`
 
 error: Unnecessary `>= y + 1` or `x - 1 >=`
   --> $DIR/int_plus_one.rs:12:13
    |
 LL |     let _ = x - 1 >= y;
-   |             ^^^^^^^^^^
-help: change `>= y + 1` to `> y` as shown
-   |
-LL |     let _ = x > y;
-   |             ^^^^^
+   |             ^^^^^^^^^^ help: change it to: `x > y`
 
 error: Unnecessary `>= y + 1` or `x - 1 >=`
   --> $DIR/int_plus_one.rs:13:13
    |
 LL |     let _ = y <= x - 1;
-   |             ^^^^^^^^^^
-help: change `>= y + 1` to `> y` as shown
-   |
-LL |     let _ = y < x;
-   |             ^^^^^
+   |             ^^^^^^^^^^ help: change it to: `y < x`
 
 error: aborting due to 4 previous errors