build: disable libsecp256k1 benchmarks

These were previously disabled, but upstream changed to having benchmarks enabled by default
in bitcoin-core/secp256k1#480 and we pulled that change as part of #15703.

Author: fanquake

configure.ac

@@ -1625,7 +1625,7 @@ if test x$need_bundled_univalue = xyes; then
   AC_CONFIG_SUBDIRS([src/univalue])
 fi
 
-ac_configure_args="${ac_configure_args} --disable-shared --with-pic --with-bignum=no --enable-module-recovery --disable-jni"
+ac_configure_args="${ac_configure_args} --disable-shared --with-pic --enable-benchmark=no --with-bignum=no --enable-module-recovery --disable-jni"
 AC_CONFIG_SUBDIRS([src/secp256k1])
 
 AC_OUTPUT