store only 3 months worth of logs instead of 6
store only 3 months worth of logs instead of 6

refs DE-1120

Change-Id: I93354c20e89dc7b6f34abee16b2b15cafa8ac356
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/288951
Reviewed-by: Bobby Buten <5d364bfede2bfc09ec31d2e6ed3a4d111d37200d@instructure.com>
QA-Review: Aaron Ogata <11ccf682c06d1508642f943a3962a1c3d00b8e44@instructure.com>
Product-Review: Aaron Ogata <11ccf682c06d1508642f943a3962a1c3d00b8e44@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms