PostgreSQL: How do I stop PostgreSQL from generating logs for PL/pgSQL functions?
The presence of CONTEXT depends on log_error_verbosity.
Another setting you might want to tune down is log_min_error_statement.
From the documentation:
log_min_error_statement (enum)

Controls which SQL statements that cause an error condition are
recorded in the server log. The current SQL statement is included in
the log entry for any message of the specified severity or higher.
Valid values are DEBUG5, DEBUG4, DEBUG3, DEBUG2, DEBUG1, INFO, NOTICE,
WARNING, ERROR, LOG, FATAL, and PANIC. The default is ERROR, which
means statements causing errors, log messages, fatal errors, or panics
will be logged. To effectively turn off logging of failing statements,
set this parameter to PANIC. Only superusers can change this setting.

log_error_verbosity (enum)

Controls the amount of detail written in the server log for each
message that is logged. Valid values are TERSE, DEFAULT, and VERBOSE,
each adding more fields to displayed messages. TERSE excludes the
logging of DETAIL, HINT, QUERY, and CONTEXT error information. VERBOSE
output includes the SQLSTATE error code (see also Appendix A) and the
source code file name, function name, and line number that generated
the error. Only superusers can change this setting.