Pretty print async block without redundant space

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2068,7 +2068,6 @@ impl<'a> State<'a> {
             ast::ExprKind::Async(capture_clause, _, ref blk) => {
                 self.word_nbsp("async");
                 self.print_capture_clause(capture_clause);
-                self.s.space();
                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
                 self.cbox(INDENT_UNIT);
                 self.ibox(0);

src/test/ui/async-await/issues/issue-54752-async-block.rs

@@ -3,5 +3,5 @@
 // edition:2018
 // pp-exact
 
-fn main() { let _a = (async  { }); }
+fn main() { let _a = (async { }); }
 //~^ WARNING unnecessary parentheses around assigned value

src/test/ui/async-await/issues/issue-54752-async-block.stderr

@@ -1,14 +1,14 @@
 warning: unnecessary parentheses around assigned value
   --> $DIR/issue-54752-async-block.rs:6:22
    |
-LL | fn main() { let _a = (async  { }); }
-   |                      ^          ^
+LL | fn main() { let _a = (async { }); }
+   |                      ^         ^
    |
    = note: `#[warn(unused_parens)]` on by default
 help: remove these parentheses
    |
-LL - fn main() { let _a = (async  { }); }
-LL + fn main() { let _a = async  { }; }
+LL - fn main() { let _a = (async { }); }
+LL + fn main() { let _a = async { }; }
    | 
 
 warning: 1 warning emitted