feat: Simplify HTTP Load Balancer grammr (#515)

Update wording from beginning up through "Limit the Number of 
Connections". Break up long sentences and clarify ambiguous wording, 
using the linked pages on https://nginx.org/en/docs/ to disambiguate.

Consistency changes throughout, favoring the wording most used in this 
document: Change all "load-balanc*" to "load balanc*" except in URLs. 
Change "parameter of" to "parameter to". 

Remove gerunds from subheadings throughout.

Co-authored-by: Mike Jang <3287976+mjang@users.noreply.github.com>

Author: Vleq