watchman: rename branch from master to main
watchman: rename branch from master to main

We recently switched our main branch from "master" to "main" and that has broken Homebrew's ability to build from HEAD. This commit fixes that.

Closes #84929.

Signed-off-by: Michael Cho <ad37dc0e034c3938811c0096de6272abd124db31@users.noreply.github.com>
Signed-off-by: BrewTestBot <8a898ee6867e4f2028e63d2a6319b2224641c06c@users.noreply.github.com>

adam-moss/homebrew-core,stgraber/homebrew-core,nbari/homebrew-core,Homebrew/homebrew-core,uyjulian/homebrew-core,zyedidia/homebrew-core,zyedidia/homebrew-core,lemzwerg/homebrew-core,uyjulian/homebrew-core,nandub/homebrew-core,lemzwerg/homebrew-core,stgraber/homebrew-core,chrisfinazzo/homebrew-core,filcab/homebrew-core,cblecker/homebrew-core,nbari/homebrew-core,Moisan/homebrew-core,chrisfinazzo/homebrew-core,makigumo/homebrew-core,sjackman/homebrew-core,mfikes/homebrew-core,cblecker/homebrew-core,Homebrew/homebrew-core,makigumo/homebrew-core,adam-moss/homebrew-core,filcab/homebrew-core,Moisan/homebrew-core,mfikes/homebrew-core,nandub/homebrew-core,sjackman/homebrew-core