Add help assertion for async pub test

Author: pickfire

src/test/ui/parser/issue-76437-async.rs

@@ -3,4 +3,5 @@
 mod t {
     async pub fn t() {}
     //~^ ERROR expected one of `extern`, `fn`, or `unsafe`, found keyword `pub`
+    //~| HELP visibility `pub` must come before `async`
 }

src/test/ui/parser/issue-76437-const-async-unsafe.rs

@@ -3,4 +3,5 @@
 mod t {
     const async unsafe pub fn t() {}
     //~^ ERROR expected one of `extern` or `fn`, found keyword `pub`
+    //~| HELP visibility `pub` must come before `const async unsafe`
 }

src/test/ui/parser/issue-76437-const-async.rs

@@ -3,4 +3,5 @@
 mod t {
     const async pub fn t() {}
     //~^ ERROR expected one of `extern`, `fn`, or `unsafe`, found keyword `pub`
+    //~| HELP visibility `pub` must come before `const async`
 }

src/test/ui/parser/issue-76437-const.rs

@@ -3,4 +3,5 @@
 mod t {
     const pub fn t() {}
     //~^ ERROR expected one of `async`, `extern`, `fn`, or `unsafe`, found keyword `pub`
+    //~| HELP visibility `pub` must come before `const`
 }

src/test/ui/parser/issue-76437-pub-crate-unsafe.rs

@@ -3,4 +3,5 @@
 mod t {
     unsafe pub(crate) fn t() {}
     //~^ ERROR expected one of `extern` or `fn`, found keyword `pub`
+    //~| HELP visibility `pub(crate)` must come before `unsafe`
 }

src/test/ui/parser/issue-76437-unsafe.rs

@@ -3,4 +3,5 @@
 mod t {
     unsafe pub fn t() {}
     //~^ ERROR expected one of `extern` or `fn`, found keyword `pub`
+    //~| HELP visibility `pub` must come before `unsafe`
 }