net/miniupnpc: fix PKG_CPE_ID

cpe:/a:miniupnp_project:miniupnpc is the correct CPE ID for miniupnpc:
https://nvd.nist.gov/products/cpe/search/results?keyword=cpe:2.3:a:miniupnp_project:miniupnpc

Fixes: 299e5b0a

 (treewide: add PKG_CPE_ID for better cvescanner coverage)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>