Reduce code duplication in zstreamtest

lib/zstd.h

@@ -1002,7 +1002,7 @@ typedef enum {
 
     /* advanced parameters - may not remain available after API update */
     ZSTD_p_forceMaxWindow=1100, /* Force back-reference distances to remain < windowSize,
-                              * even when referencing into Dictionary content (default:0) */
+                                 * even when referencing into Dictionary content (default:0) */
 
 } ZSTD_cParameter;