feat postgres: update default value for sync-start in description

Tests: протестировано CI
commit_hash:44ff793bb344a31ac2d51e1de19dc55c6ea173f7

Author: apolukhin

postgresql/include/userver/storages/postgres/component.hpp

@@ -120,7 +120,7 @@ namespace components {
 /// dbconnection            | connection DSN string (used if no dbalias specified)                          | --
 /// blocking_task_processor | name of task processor for background blocking operations                     | --
 /// max_replication_lag     | replication lag limit for usable slaves                                       | 60s
-/// sync-start              | perform initial connections synchronously                                     | false
+/// sync-start              | perform initial connections synchronously                                     | true
 /// dns_resolver            | server hostname resolver type (getaddrinfo or async)                          | 'async'
 /// persistent-prepared-statements | cache prepared statements or not                                       | true
 /// user-types-enabled      | allow use of user-defined types                                               | true