[calls] HACKING: Fix style around signals

[Evangelos Ribeiro Tzaras <devrtz src gnome org>]

commit 41fe9033ac921df5d8365e919db1eecaee9b5c86
Author: Evangelos Ribeiro Tzaras <evangelos tzaras puri sm>
Date:   Tue Jul 13 18:52:49 2021 +0200

    HACKING: Fix style around signals
    
    We actually never used the array initialization as suggested.

 HACKING.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/HACKING.md b/HACKING.md
index f8b6f6ff..42356a9b 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -95,7 +95,7 @@ individual C files should be structured as (top to bottom of file):
       BAR_TRIGGERED,
       N_SIGNALS
     };
-    static guint signals[N_SIGNALS] = { 0 };
+    static guint signals[N_SIGNALS];
     ```
   - type definitions
     ```c