CLEANUP: Do not use a fixed type for 'sizeof' in 'calloc'

Changes performed using the following coccinelle patch:

    @@
    type T;
    expression E;
    expression t;
    @@

    (
      t = calloc(E, sizeof(*t))
    |
    - t = calloc(E, sizeof(T))
    + t = calloc(E, sizeof(*t))
    )

Looking through the commit history, grepping for coccinelle shows that the same
replacement with a different patch was already performed in the past in commit
02779b6263a177b1e462e53db6eaf57bcda574bc.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 64c86b1..b8d6b4c 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -5107,7 +5107,7 @@
 	}
 
 	/* Allocate cert structure */
-	ckch = calloc(1, sizeof(struct cert_key_and_chain));
+	ckch = calloc(1, sizeof(*ckch));
 	if (!ckch) {
 		ha_alert("Proxy '%s': Failed to read CA certificate file '%s' at [%s:%d]. Chain allocation failure\n",
 			px->id, bind_conf->ca_sign_file, bind_conf->file, bind_conf->line);