Rewinds the descriptor's next-index counter by one.
Declared in <wallet/scriptpubkeyman.h>
[[requires_capability(0x7fd7419bb198), requires_capability(0x7fd7453dbba8), requires_capability(0x7fd73d7928a8), requires_capability(0x7fd745b556f8), requires_capability(0x7fd75f7ec6e8), requires_capability(0x7fd738e43c08)]]
void
DecIndex();