Suggests compiler to update if on older version when using unstable feature

Part of Issue #117318

Author: Rajveer100

Diff for: compiler/rustc_hir_analysis/messages.ftl

@@ -151,6 +151,7 @@ hir_analysis_missing_trait_item_unstable = not all trait items implemented, miss
     .note = default implementation of `{$missing_item_name}` is unstable
     .some_note = use of unstable library feature '{$feature}': {$reason}
     .none_note = use of unstable library feature '{$feature}'
+    .note = if you are on an old compiler version you may need to update your compiler
 
 hir_analysis_missing_type_params =
     the type {$parameterCount ->