Use the canonical way of splitting name, version

Mozilla website uses rsplit to extract the name and version so it should
be better in any case.
https://github.com/mozilla/bedrock/blob/765a60450235d810cf941676e4a29f012a9eaaba/bedrock/security/models.py#L29
Based on discussion here
mozilla/foundation-security-advisories#76

Signed-off-by: Hritik Vijay <hritikxx8@gmail.com>

vulnerabilities/importers/mozilla.py

@@ -130,10 +130,9 @@ def get_package_urls(self, pkgs: List[str]) -> List[PackageURL]:
         package_urls = [
             PackageURL(
                 type="mozilla",
-                # TODO: Improve after https://github.com/mozilla/foundation-security-advisories/issues/76#issuecomment-803082182
                 # pkg is of the form "Firefox ESR 1.21" or "Thunderbird 2.21"
-                name=" ".join(pkg.split(" ")[0:-1]),
-                version=pkg.split(" ")[-1],
+                name=pkg.rsplit(None, 1)[0],
+                version=pkg.rsplit(None, 1)[1],
             )
             for pkg in pkgs
         ]