Merge bitcoin#27420: build: remove ancient unused define

9fbc5fc build: remove ancient unused define (Cory Fields)

Pull request description:

  The generic define was removed in [upstream miniupnpc in 2014](miniupnp/miniupnp@f6774e3).

  Noticed while reviewing hebasto's new CMake buildsystem: hebasto#12 (comment).

ACKs for top commit:
  RandyMcMillan:
    utACK 9fbc5fc
  hebasto:
    ACK 9fbc5fc
  TheCharlatan:
    ACK 9fbc5fc

Tree-SHA512: 2075a2e63441e32d939c23f30f811c73dd1ab1ddcc9e6bf079cc8060e77d9a2a6d707add7b72e9251939a53b53e28a134e9bb330ccf3556244497728f1b091ae

Author: fanquake

configure.ac

@@ -1694,7 +1694,7 @@ else
     use_upnp=yes
     AC_DEFINE([USE_UPNP], [1], [Define to 1 if UPnP support should be compiled in.])
     if test "$TARGET_OS" = "windows"; then
-      MINIUPNPC_CPPFLAGS="$MINIUPNPC_CPPFLAGS -DSTATICLIB -DMINIUPNP_STATICLIB"
+      MINIUPNPC_CPPFLAGS="$MINIUPNPC_CPPFLAGS -DMINIUPNP_STATICLIB"
     fi
   else
     AC_MSG_RESULT([no])