patch 8.2.4241: some type casts are redundant

Problem:    Some type casts are redundant.
Solution:   Remove the type casts. (closes #9643)
diff --git a/src/if_cscope.c b/src/if_cscope.c
index 9e0ec45..edcd4ca 100644
--- a/src/if_cscope.c
+++ b/src/if_cscope.c
@@ -916,7 +916,7 @@
 	    goto err_closing;
 #endif
 	}
-	expand_env((char_u *)p_csprg, (char_u *)prog, MAXPATHL);
+	expand_env(p_csprg, (char_u *)prog, MAXPATHL);
 
 	// alloc space to hold the cscope command
 	len = (int)(strlen(prog) + strlen(csinfo[i].fname) + 32);