maxIndexBuildMemoryUsageMegabytes default is 200mb for recent versions of 4.2 and 4.4

Description

Docs for maxIndexBuildMemoryUsageMegabytes state that the default is 500mb, but it changed from 500mb to 200mb in 4.2.3 and is also 200mb in 4.4.0rc0

This value was recently changed in 4.4, and then the change was reverted, so it would be good for the code owners to confirm this will remain at 200mb

There are several references to 500mb in the 4.2 docs and 4.4 docs. The first place to start are the docs for the parameter in 4.2 and in 4.4

A simple test case is:

db.f.insert({a:1})

db.f.createIndex({a:1})

Then grep the mongod.log for "bytes"

# from 4.0.17

...  building index using bulk method; build may temporarily use up to 500 megabytes of RAM

# from 4.2.2

... build may temporarily use up to 500 megabytes of RAM

# from 4.2.3 and 4.4.0rc0

...  build may temporarily use up to 200 megabytes of RAM

Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)