Remove "maxOfferConcurrency" and "offerBackoffLimit" from config file as they are deprecated

[MeijeSibbel]

Package Versions

Replace the values below using the output from storjshare --version.

2.0.3

Replace the values below using the output from node --version.

6.9.1

Expected Behavior

As both "maxOfferConcurrency" and "offerBackoffLimit" are deprecated, remove them from the JSON structure when creating a new node.

Actual Behavior

Please describe the program's actual behavior. Please include any stack traces
or log output in the back ticks below.

These two parameters are added to the config file even though they are deprecated.

Steps to Reproduce

Please include the steps the reproduce the issue, numbered below. Include as
much detail as possible.

1. ...
2. ...
3. ...

[Puychack]

Is there any new setting that replaces the old ones ?

[MeijeSibbel]

@littleskunk , are you sure this is not deprecated?

[littleskunk]

@MeijeSibbel yes I am sure.
https://github.com/Storj/core/blob/eb006a04a355465f9419bf779c23beb93e58a6fe/lib/network/farmer.js#L126

Only maxOfferConcurrency can be removed.