push: make the parallelism default follow the docs

include/git2/remote.h

@@ -643,7 +643,7 @@ typedef struct {
 } git_push_options;
 
 #define GIT_PUSH_OPTIONS_VERSION 1
-#define GIT_PUSH_OPTIONS_INIT { GIT_PUSH_OPTIONS_VERSION, 0, GIT_REMOTE_CALLBACKS_INIT, GIT_PROXY_OPTIONS_INIT }
+#define GIT_PUSH_OPTIONS_INIT { GIT_PUSH_OPTIONS_VERSION, 1, GIT_REMOTE_CALLBACKS_INIT, GIT_PROXY_OPTIONS_INIT }
 
 /**
  * Initialize git_push_options structure