tests/ui/hello_world/main.rs: Remove FIXME

The purpose of the test is to make sure that compiling hello world
produces no compiler output. To properly test that, we need to run the
entire compiler pipeline. We don't want the test to pass if codegen
accidentally starts writing to stdout. So keep it as build-pass.

tests/ui/hello_world/main.rs

@@ -1,4 +1,4 @@
-// build-pass (FIXME(62277): could be check-pass?)
+// build-pass
 
 // Test that compiling hello world succeeds with no output of any kind.