docs: remove double spacing (#635)

Co-authored-by: Renan <[email protected]>

Author: alestiago

docs/docs/advanced/security_context.md

@@ -16,7 +16,7 @@ Future<HttpServer> run(Handler handler, InternetAddress ip, int port) {
   final chain = Platform.script.resolve('certificates/server_chain.pem').toFilePath();
   final key = Platform.script.resolve('certificates/server_key.pem').toFilePath();
 
-  final securityContext =  SecurityContext()
+  final securityContext = SecurityContext()
     ..useCertificateChain(chain)
     ..usePrivateKey(key, password: 'VeryGoodPassword');