docs: Update git-guide with tools/clean-branches.
docs: Update git-guide with tools/clean-branches.

shubhamdhama/zulip,punchagan/zulip,amanharitsh123/zulip,showell/zulip,zulip/zulip,verma-varsha/zulip,showell/zulip,timabbott/zulip,jackrzhang/zulip,zulip/zulip,vabs22/zulip,Galexrt/zulip,punchagan/zulip,kou/zulip,hackerkid/zulip,verma-varsha/zulip,zulip/zulip,vabs22/zulip,synicalsyntax/zulip,shubhamdhama/zulip,jackrzhang/zulip,amanharitsh123/zulip,rht/zulip,shubhamdhama/zulip,rishig/zulip,andersk/zulip,eeshangarg/zulip,mahim97/zulip,eeshangarg/zulip,rht/zulip,shubhamdhama/zulip,amanharitsh123/zulip,rishig/zulip,verma-varsha/zulip,andersk/zulip,jackrzhang/zulip,kou/zulip,vaidap/zulip,eeshangarg/zulip,zulip/zulip,mahim97/zulip,Galexrt/zulip,shubhamdhama/zulip,rht/zulip,brainwane/zulip,vabs22/zulip,dhcrzf/zulip,jrowan/zulip,showell/zulip,verma-varsha/zulip,dhcrzf/zulip,jrowan/zulip,brainwane/zulip,vabs22/zulip,vabs22/zulip,brockwhittaker/zulip,synicalsyntax/zulip,dhcrzf/zulip,vaidap/zulip,brainwane/zulip,jrowan/zulip,timabbott/zulip,verma-varsha/zulip,shubhamdhama/zulip,rishig/zulip,showell/zulip,andersk/zulip,punchagan/zulip,synicalsyntax/zulip,andersk/zulip,shubhamdhama/zulip,jackrzhang/zulip,tommyip/zulip,Galexrt/zulip,brockwhittaker/zulip,brainwane/zulip,amanharitsh123/zulip,rht/zulip,vabs22/zulip,tommyip/zulip,amanharitsh123/zulip,kou/zulip,mahim97/zulip,showell/zulip,brockwhittaker/zulip,andersk/zulip,punchagan/zulip,Galexrt/zulip,eeshangarg/zulip,brainwane/zulip,hackerkid/zulip,hackerkid/zulip,hackerkid/zulip,vaidap/zulip,punchagan/zulip,showell/zulip,eeshangarg/zulip,mahim97/zulip,zulip/zulip,hackerkid/zulip,kou/zulip,punchagan/zulip,timabbott/zulip,punchagan/zulip,rishig/zulip,brainwane/zulip,synicalsyntax/zulip,brockwhittaker/zulip,timabbott/zulip,andersk/zulip,showell/zulip,synicalsyntax/zulip,vaidap/zulip,vaidap/zulip,kou/zulip,dhcrzf/zulip,mahim97/zulip,synicalsyntax/zulip,Galexrt/zulip,Galexrt/zulip,kou/zulip,jackrzhang/zulip,jrowan/zulip,jrowan/zulip,jackrzhang/zulip,tommyip/zulip,Galexrt/zulip,zulip/zulip,hackerkid/zulip,rishig/zulip,rishig/zulip,synicalsyntax/zulip,rht/zulip,timabbott/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,jrowan/zulip,brainwane/zulip,dhcrzf/zulip,vaidap/zulip,amanharitsh123/zulip,brockwhittaker/zulip,eeshangarg/zulip,jackrzhang/zulip,tommyip/zulip,tommyip/zulip,andersk/zulip,tommyip/zulip,rht/zulip,timabbott/zulip,verma-varsha/zulip,tommyip/zulip,mahim97/zulip,rishig/zulip,zulip/zulip,dhcrzf/zulip,timabbott/zulip,dhcrzf/zulip,rht/zulip,brockwhittaker/zulip