chore: Remove unknown annotation warning (#5531)

# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

Removes the "Unknown attribute warning" since it is now spamming
aztec-nr use cases.

## Additional Context

We'll want to re-add this warning eventually but we'd need some way to
known when users want to call attributes as a function versus when they
are just annotations picked up from elsewhere. It's possible this later
use case may disappear once `macro_processors` is removed though.

## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

compiler/noirc_frontend/src/elaborator/mod.rs

@@ -1311,9 +1311,10 @@ impl<'context> Elaborator<'context> {
         let (function_name, mut arguments) = Self::parse_attribute(attribute, location)
             .unwrap_or_else(|| (attribute.to_string(), Vec::new()));
 
-        let id = self
-            .lookup_global(Path::from_single(function_name, span))
-            .map_err(|_| (ResolverError::UnknownAnnotation { span }.into(), self.file))?;
+        let Ok(id) = self.lookup_global(Path::from_single(function_name, span)) else {
+            // Do not issue an error if the attribute is unknown
+            return Ok(());
+        };
 
         let definition = self.interner.definition(id);
         let DefinitionKind::Function(function) = definition.kind else {