Update max milestone threshold value

[laumair]

Description

• Update wallet's default node to https://nodes.iota.org
• Update max milestone threshold value. Max milestone threshold is the value used for node sync checks. This value determines how far behind in milestones a node can be. Previously, it was set to 1 which is quite restrictive and often leads to "out of sync" errors.

Type of change

• Enhancement (a non-breaking change which adds functionality)

How Has This Been Tested?

• Updated unit tests

Checklist:

• My code follows the style guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• For changes to mobile that include native code (including React Native modules): I have verified that both iOS and Android successfully build in both Debug and Release modes
• For changes to shared: If applicable, I have verified that my changes are implemented correctly in desktop and mobile