build: remove --enable-experimental from libsecp256k1 configure

Author: fanquake

configure.ac

@@ -1967,7 +1967,7 @@ PKGCONFIG_LIBDIR_TEMP="$PKG_CONFIG_LIBDIR"
 unset PKG_CONFIG_LIBDIR
 PKG_CONFIG_LIBDIR="$PKGCONFIG_LIBDIR_TEMP"
 
-ac_configure_args="${ac_configure_args} --disable-shared --with-pic --enable-benchmark=no --enable-module-recovery --enable-module-schnorrsig --enable-experimental"
+ac_configure_args="${ac_configure_args} --disable-shared --with-pic --enable-benchmark=no --enable-module-recovery --enable-module-schnorrsig"
 AC_CONFIG_SUBDIRS([src/secp256k1])
 
 AC_OUTPUT