Change default thread count from 100 to 10.

[skynetcap]

• Fixes default thread count from 100 to 10, as initially specified in code comments.

From the code comments:

/// * "threads" optional, specifies the number of worker threads for the plugin. A thread
/// maintains a PostgreSQL connection to the server. The default is '10'.

[skynetcap]

Given that the optimal thread count is usually based on the number of physical cores, on my validator I've experienced greatly improved performance by using a value of 32 threads. Given that most validator should have that as a minimum, it may be worth increasing this default value to 32.