Mark flint++ as deprecated

Carlos López · Carlos López · commit 8f977131e069 · 2024-08-16T10:13:09.000+02:00
The flint++ repository is archived as of August 2023, so mark the tool
as deprecated.
diff --git a/data/tools/flint.yml b/data/tools/flint.yml
@@ -4,6 +4,7 @@ categories:
 tags:
   - c
   - cpp
+deprecated: true
 license: Boost Software License 1.0
 types:
   - cli
