[flang][docs] Correct the title in Unsigned.md (#171553)

kawashima-fj · web-flow · commit 17b13e9e3f43 · 2025-12-10T11:42:32.000+09:00
Probablly the original author copied `Extensions.md` and forgot to
change the title.
diff --git a/flang/docs/Unsigned.md b/flang/docs/Unsigned.md
@@ -6,7 +6,7 @@
   
 -->
 
-# Fortran Extensions supported by Flang
+# Flang support for UNSIGNED type
 
 ```{contents}
 ---
