Fix several minor issues on the seclang grammar

src/actions/action.cc

@@ -76,9 +76,6 @@ Action *Action::instantiate(const std::string& name) {
     if (name.compare(0, rule_id.length(), rule_id) == 0) {
         return new RuleId(name);
     }
-    if (name.compare(0, severity.length(), severity) == 0) {
-        return new Severity(name);
-    }
     if (name == "chain") {
         return new Chain(name);
     }

src/actions/severity.cc

@@ -28,7 +28,6 @@ namespace actions {
 Severity::Severity(std::string action)
     : Action(action, RunTimeOnlyIfMatchKind) {
     std::string a = action;
-    a.erase(0, 9);
     if (tolower(a) == "emergency") {
         this->m_severity = 0;
     } else if (tolower(a) == "alert") {