[AIRFLOW-3111] Fix instructions in UPDATING.md and remove comment (#3944)

artifacts in default_airflow.cfg

- fixed incorrect instructions in UPDATING.md regarding core.log_filename_template and elasticsearch.elasticsearch_log_id_template
- removed comments referencing "additional curly braces" from
default_airflow.cfg since they're irrelevant to the rendered airflow.cfg

UPDATING.md

@@ -134,11 +134,11 @@ With Airflow 1.9 or lower, `FILENAME_TEMPLATE`, `PROCESSOR_FILENAME_TEMPLATE`, `
 ```
 [core]
 fab_logging_level = WARN
-log_filename_template = {{{{ ti.dag_id }}}}/{{{{ ti.task_id }}}}/{{{{ ts }}}}/{{{{ try_number }}}}.log
-log_processor_filename_template = {{{{ filename }}}}.log
+log_filename_template = {{ ti.dag_id }}/{{ ti.task_id }}/{{ ts }}/{{ try_number }}.log
+log_processor_filename_template = {{ filename }}.log
 
 [elasticsearch]
-elasticsearch_log_id_template = {{dag_id}}-{{task_id}}-{{execution_date}}-{{try_number}}
+elasticsearch_log_id_template = {dag_id}-{task_id}-{execution_date}-{try_number}
 elasticsearch_end_of_log_mark = end_of_log
 ```
 

airflow/config_templates/default_airflow.cfg

@@ -62,12 +62,10 @@ fab_logging_level = WARN
 logging_config_class =
 
 # Log format
-# we need to escape the curly braces by adding an additional curly brace
 log_format = [%%(asctime)s] {{%%(filename)s:%%(lineno)d}} %%(levelname)s - %%(message)s
 simple_log_format = %%(asctime)s %%(levelname)s - %%(message)s
 
 # Log filename format
-# we need to escape the curly braces by adding an additional curly brace
 log_filename_template = {{{{ ti.dag_id }}}}/{{{{ ti.task_id }}}}/{{{{ ts }}}}/{{{{ try_number }}}}.log
 log_processor_filename_template = {{{{ filename }}}}.log
 
@@ -561,7 +559,6 @@ hide_sensitive_variable_fields = True
 
 [elasticsearch]
 elasticsearch_host =
-# we need to escape the curly braces by adding an additional curly brace
 elasticsearch_log_id_template = {{dag_id}}-{{task_id}}-{{execution_date}}-{{try_number}}
 elasticsearch_end_of_log_mark = end_of_log