tools/expat: fix PKG_CPE_ID
cpe:/a:libexpat_project:libexpat is the correct CPE ID for expat:
https://nvd.nist.gov/products/cpe/search/results?keyword=cpe:2.3:a:libexpat:libexpat
Fixes: c61a2395140d92cdd37d3d6ee43a765427e8e318 (add PKG_CPE_ID ids to package and tools)
Signed-off-by: Fabrice Fontaine <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/15291
Signed-off-by: Robert Marko <[email protected]>