truststore_linux: remove PATH check for SystemTrustCommand

It's hard to predict what the PATH that sudo will use, and there
shouldn't be many cases where we don't find the command anyway.

Fixes #188

truststore_linux.go

@@ -45,9 +45,6 @@ func init() {
 		SystemTrustFilename = "/usr/share/pki/trust/anchors/%s.pem"
 		SystemTrustCommand = []string{"update-ca-certificates"}
 	}
-	if SystemTrustCommand != nil && !binaryExists(SystemTrustCommand[0]) {
-		SystemTrustCommand = nil
-	}
 }
 
 func (m *mkcert) systemTrustFilename() string {