docs: Clean redundant fragment links to the same page.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

docs/development/setup-vagrant.md

@@ -830,7 +830,7 @@ Likely causes are:
 1. Networking issues
 2. Insufficient RAM. Check whether you've allotted at least two
    gigabytes of RAM, which is the minimum Zulip
-   [requires](../development/setup-vagrant.html#requirements). If
+   [requires](#requirements). If
    not, go to your VM settings and increase the RAM, then restart
    the VM.
 

docs/git/using.md

@@ -452,6 +452,6 @@ complicated rebase.
 [github-help-sync-fork]: https://help.github.com/en/articles/syncing-a-fork
 [how-git-is-different]: ./the-git-difference.md
 [self-multiple-computers]: ../git/troubleshooting.html#working-from-multiple-computers
-[zulip-git-guide-up-to-date]: ../git/using.html#keep-your-fork-up-to-date
+[zulip-git-guide-up-to-date]: #keep-your-fork-up-to-date
 [zulip-rtd-commit-discipline]: ../contributing/version-control.html#commit-discipline
 [zulip-rtd-commit-messages]: ../contributing/version-control.html#commit-messages

docs/production/deployment.md

@@ -221,7 +221,7 @@ configure that as follows:
 We also have documentation for a Zulip server [using HTTP][using-http] for use
 behind reverse proxies.
 
-[using-http]: ../production/deployment.html#configuring-zulip-to-allow-http
+[using-http]: #configuring-zulip-to-allow-http
 
 ## Customizing the outgoing HTTP proxy