detect-engine: remove redundant configuration check

src/detect-engine.c

@@ -2440,12 +2440,10 @@ retry:
 
 bool DetectEngineMpmCachingEnabled(void)
 {
-    const char *strval = NULL;
-    if (SCConfGet("detect.sgh-mpm-caching", &strval) != 1)
-        return false;
-
     int sgh_mpm_caching = 0;
-    (void)SCConfGetBool("detect.sgh-mpm-caching", &sgh_mpm_caching);
+    if (SCConfGetBool("detect.sgh-mpm-caching", &sgh_mpm_caching) != 1) {
+        return false;
+    }
     return (bool)sgh_mpm_caching;
 }