contrib/make_libsecp256k1.sh: rm Makefile patch

unneeded since c0cd7de6d4
and in fact buggy since 0bd3e4243c

related https://github.com/spesmilo/electrum/pull/8185#issuecomment-1416171287

contrib/make_libsecp256k1.sh

@@ -43,7 +43,6 @@ info "Building $pkgname..."
     git checkout "${LIBSECP_VERSION}^{commit}"
 
     if ! [ -x configure ] ; then
-        echo "libsecp256k1_la_LDFLAGS = -no-undefined" >> Makefile.am
         echo "LDFLAGS = -no-undefined" >> Makefile.am
         ./autogen.sh || fail "Could not run autogen for $pkgname. Please make sure you have automake and libtool installed, and try again."
     fi