Changes limit for lsif artifacts to 100MB

What does this MR do?

Related issue: #249561 (closed)

After the recent fix of the in-memory processing, the memory usage reduced significantly for a large file, maybe we can try increasing the limit without waiting for gitlab-workhorse#270 (moved).

Up:

== 20201105135051 ChangeDefaultValueOfCiMaxArtifactSizeLsifOfPlanLimitsFrom20To100: migrating
-- change_column_default(:plan_limits, :ci_max_artifact_size_lsif, 100)
   -> 0.0133s
-- execute("UPDATE plan_limits SET ci_max_artifact_size_lsif = 100 WHERE ci_max_artifact_size_lsif = 20")
   -> 0.0063s
== 20201105135051 ChangeDefaultValueOfCiMaxArtifactSizeLsifOfPlanLimitsFrom20To100: migrated (0.0316s)

Down:

== 20201105135051 ChangeDefaultValueOfCiMaxArtifactSizeLsifOfPlanLimitsFrom20To100: reverting
-- change_column_default(:plan_limits, :ci_max_artifact_size_lsif, 20)
   -> 0.0072s
-- execute("UPDATE plan_limits SET ci_max_artifact_size_lsif = 20 WHERE ci_max_artifact_size_lsif = 100")
   -> 0.0007s
== 20201105135051 ChangeDefaultValueOfCiMaxArtifactSizeLsifOfPlanLimitsFrom20To100: reverted (0.0134s)