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/extcheck.c b/src/extcheck.c
index 721e49d..e6b30ff 100644
--- a/src/extcheck.c
+++ b/src/extcheck.c
@@ -274,13 +274,13 @@
 		}
 
 	check->curpid = NULL;
-	check->envp = calloc((EXTCHK_SIZE + 1), sizeof(char *));
+	check->envp = calloc((EXTCHK_SIZE + 1), sizeof(*check->envp));
 	if (!check->envp) {
 		ha_alert("Failed to allocate memory for environment variables. Aborting\n");
 		goto err;
 	}
 
-	check->argv = calloc(6, sizeof(char *));
+	check->argv = calloc(6, sizeof(*check->argv));
 	if (!check->argv) {
 		ha_alert("Starting [%s:%s] check: out of memory.\n", px->id, s->id);
 		goto err;