Fix TOYBOX_VERSION

The latest tagged version is 0.7.1.
diff --git a/main.c b/main.c
index eeae2f3..bedb333 100644
--- a/main.c
+++ b/main.c
@@ -6,7 +6,7 @@
 #include "toys.h"
 
 #ifndef TOYBOX_VERSION
-#define TOYBOX_VERSION "0.7.0"
+#define TOYBOX_VERSION "0.7.1"
 #endif
 
 // Populate toy_list[].