Use rustc_fluent_macro::fluent_messages! directly.

Currently we always do this:
```
use rustc_fluent_macro::fluent_messages;
...
fluent_messages! { "./example.ftl" }
```
But there is no need, we can just do this everywhere:
```
rustc_fluent_macro::fluent_messages! { "./example.ftl" }
```
which is shorter.

compiler/rustc_hir_analysis/src/lib.rs

@@ -99,7 +99,6 @@ pub mod structured_errors;
 mod variance;
 
 use rustc_errors::ErrorGuaranteed;
-use rustc_fluent_macro::fluent_messages;
 use rustc_hir as hir;
 use rustc_middle::middle;
 use rustc_middle::query::Providers;
@@ -114,7 +113,7 @@ use astconv::{AstConv, OnlySelfBounds};
 use bounds::Bounds;
 use rustc_hir::def::DefKind;
 
-fluent_messages! { "../messages.ftl" }
+rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 fn require_c_abi_if_c_variadic(tcx: TyCtxt<'_>, decl: &hir::FnDecl<'_>, abi: Abi, span: Span) {
     const CONVENTIONS_UNSTABLE: &str = "`C`, `cdecl`, `aapcs`, `win64`, `sysv64` or `efiapi`";