fixup! SECURITY.md: document Git for Windows' policies

The `SECURITY.md` document mentions Git for Windows' snapshots and
helpfully provides a link.

For almost eight years, these snapshots were hosted at
https://wingit.blob.core.windows.net/files/index.html, i.e. on Azure
Blobs.

As of a combination of PRs [*1*], [*2*],
snapshots are not only now built and deployed via GitHub Actions instead
of Azure Pipelines (and ARM64 artifacts are now included, too), they are
also hosted on GitHub [*3*], with the main page being hosted on GitHub
Pages [*4*].

Therefore, the original link now redirects to a new location (which is
also a lot easier to remember): http://gitforwindows.org/git-snapshots.
Let's adjust the link to link there directly.

References:
*1*: git-for-windows/git-for-windows-automation#109
*2*: git-for-windows/gfw-helper-github-app#117
*3*: https://github.com/git-for-windows/git-snapshots/releases/
*4*: https://github.com/git-for-windows/git-snapshots/commits/gh-pages

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

SECURITY.md

@@ -56,7 +56,7 @@ Note: there is currently a bug in the "Check daily for updates" code, where it m
 
 ## Snapshot versions ('nightly builds')
 
-Git for Windows also provides snapshots (these are not releases) of the current development as per git-for-Windows/git's `master` branch at the [Snapshots](https://wingit.blob.core.windows.net/files/index.html) page. This link is also listed in the footer of the [Git for Windows](https://gitforwindows.org/) home page.
+Git for Windows also provides snapshots (these are not releases) of the current development as per git-for-Windows/git's `master` branch at the [Snapshots](https://gitforwindows.org/git-snapshots/) page. This link is also listed in the footer of the [Git for Windows](https://gitforwindows.org/) home page.
 
 Note: even if those builds are not exactly "nightly", they are sometimes referred to as "nightly builds" to keep with other projects' nomenclature.