Revert "Configure log level to info by default (#267)" (#307)

## Changes

This reverts commit e7a7e5b95a.

Job and pipeline runs print progress information now. No need to
continue to rely on logging for this.

## Tests

libs/flags/log_level_flag.go

@@ -25,9 +25,7 @@ type LogLevelFlag struct {
 
 func NewLogLevelFlag() LogLevelFlag {
 	return LogLevelFlag{
-		// Note: we log at INFO level by default until
-		// we implement progress reporting to stdout/stderr.
-		l: log.LevelInfo,
+		l: log.LevelDisabled,
 	}
 }
 

libs/flags/log_level_flag_test.go

@@ -10,8 +10,8 @@ import (
 
 func TestLogLevelFlagDefault(t *testing.T) {
 	f := NewLogLevelFlag()
-	assert.Equal(t, log.LevelInfo, f.Level())
-	assert.Equal(t, "info", f.String())
+	assert.Equal(t, log.LevelDisabled, f.Level())
+	assert.Equal(t, "disabled", f.String())
 }
 
 func TestLogLevelFlagSetValid(t *testing.T) {