docs: Fix broken anchor links to troubleshooting section.
docs: Fix broken anchor links to troubleshooting section.

The Vagrant environment setup tutorial anchor links for the
Troubleshooting & Common Errors section don't work in GitHub flavored
markdown because the ampersand in the heading gets removed and the
resulting space is filled with a hyphen. (See here:
https://gist.github.com/asabaylus/3071099#gistcomment-1593627)

To make anchor links work with ReadTheDocs as well as with GitHub
markdown for the time being, this commit changes ampersand in the
heading to 'and'.

Fixes #7056.

kou/zulip,shubhamdhama/zulip,rishig/zulip,punchagan/zulip,rht/zulip,rht/zulip,zulip/zulip,brainwane/zulip,shubhamdhama/zulip,synicalsyntax/zulip,jackrzhang/zulip,rht/zulip,hackerkid/zulip,mahim97/zulip,brockwhittaker/zulip,synicalsyntax/zulip,Galexrt/zulip,brockwhittaker/zulip,punchagan/zulip,timabbott/zulip,rht/zulip,brockwhittaker/zulip,brockwhittaker/zulip,jackrzhang/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,brainwane/zulip,hackerkid/zulip,showell/zulip,kou/zulip,kou/zulip,showell/zulip,tommyip/zulip,showell/zulip,hackerkid/zulip,andersk/zulip,eeshangarg/zulip,dhcrzf/zulip,zulip/zulip,timabbott/zulip,shubhamdhama/zulip,dhcrzf/zulip,hackerkid/zulip,kou/zulip,Galexrt/zulip,kou/zulip,Galexrt/zulip,andersk/zulip,synicalsyntax/zulip,jackrzhang/zulip,jackrzhang/zulip,mahim97/zulip,punchagan/zulip,rishig/zulip,andersk/zulip,kou/zulip,punchagan/zulip,tommyip/zulip,eeshangarg/zulip,dhcrzf/zulip,Galexrt/zulip,rishig/zulip,andersk/zulip,brockwhittaker/zulip,hackerkid/zulip,mahim97/zulip,brainwane/zulip,zulip/zulip,jackrzhang/zulip,shubhamdhama/zulip,mahim97/zulip,timabbott/zulip,timabbott/zulip,punchagan/zulip,dhcrzf/zulip,showell/zulip,rishig/zulip,andersk/zulip,tommyip/zulip,showell/zulip,mahim97/zulip,synicalsyntax/zulip,synicalsyntax/zulip,tommyip/zulip,zulip/zulip,brainwane/zulip,brockwhittaker/zulip,timabbott/zulip,tommyip/zulip,showell/zulip,dhcrzf/zulip,eeshangarg/zulip,synicalsyntax/zulip,brainwane/zulip,tommyip/zulip,hackerkid/zulip,rishig/zulip,jackrzhang/zulip,jackrzhang/zulip,hackerkid/zulip,rishig/zulip,punchagan/zulip,Galexrt/zulip,rht/zulip,shubhamdhama/zulip,eeshangarg/zulip,Galexrt/zulip,brainwane/zulip,timabbott/zulip,andersk/zulip,punchagan/zulip,rht/zulip,Galexrt/zulip,showell/zulip,shubhamdhama/zulip,eeshangarg/zulip,mahim97/zulip,synicalsyntax/zulip,rht/zulip,zulip/zulip,rishig/zulip,dhcrzf/zulip,kou/zulip,timabbott/zulip,shubhamdhama/zulip,tommyip/zulip,brainwane/zulip,zulip/zulip,dhcrzf/zulip,zulip/zulip