[TechDebt] rename Git default branch to main

[rheone]

Description

"The Internet Engineering Task Force (IETF) points out that "Master-slave is an oppressive metaphor that will and should never become fully detached from history" as well as "In addition to being inappropriate and arcane, the master-slave metaphor is both technically and historically inaccurate." There's lots of more accurate options depending on context and it costs me nothing to change my vocabulary, especially if it is one less little speed bump to getting a new person excited about tech." - Scott Hanselman

Impact

This can/will affect builds. All external items pointing to master branch should be updated.