macros: fix clippy::semicolon_if_nothing_returned

Beginning from version 0.1.54 (or earlier)
`clippy::semicolon_if_nothing_returned` braked by macroses `tokio::test`
and `tokio::main` on functions without result type.

Adding semicolon into function wrappers fix it.

Fixes: rust-lang/rust-clippy#7438

tokio-macros/src/entry.rs

@@ -321,6 +321,12 @@ fn parse_knobs(
         quote! {}
     };
 
+    let tail_semicolon = match input.sig.output {
+        syn::ReturnType::Default => quote! {
+            ;
+        },
+        syn::ReturnType::Type(..) => quote! {},
+    };
     let body = &input.block;
     let brace_token = input.block.brace_token;
     input.block = syn::parse2(quote_spanned! {last_stmt_end_span=>
@@ -331,7 +337,7 @@ fn parse_knobs(
                 .enable_all()
                 .build()
                 .expect("Failed building the Runtime")
-                .block_on(body)
+                .block_on(body)#tail_semicolon
         }
     })
     .expect("Parsing failure");