bmcweb: remove NEW_BOOST_URL

The BOOST URL upgrade has been finished for a while.
The macro was removed in
https://github.com/openbmc/bmcweb/commit/50b8a43af501412f93a93ccce34a9ea7abb6d57f

This change simply drops the macro given that no codes reference it at
HEDA.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I3f60afd86906037b7207ea01aba78aafbeaf6daa
diff --git a/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb b/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb
index ce9a39f..57e5f01 100644
--- a/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb
+++ b/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb
@@ -17,8 +17,6 @@
 
 S = "${WORKDIR}/git"
 
-CXXFLAGS:append = " -DNEW_BOOST_URL"
-
 inherit pkgconfig meson ptest
 
 SRC_URI += " \