Update libsodium download URL

Summary:
Old libsodium downloads moved to a different URL breaking the build, e.g. https://github.com/facebook/fbthrift/actions/runs/9464211012/job/26071044729:

```
Download with https://download.libsodium.org/libsodium/releases/old/libsodium-1.0.17-msvc.zip -> Z:\downloads\libsodium-libsodium-1.0.17-msvc.zip ...
TransientFailure: Failed to download https://download.libsodium.org/libsodium/releases/old/libsodium-1.0.17-msvc.zip to Z:\downloads\libsodium-libsodium-1.0.17-msvc.zip: HTTP Error 404: Not Found
```

Fix it.

Reviewed By: bigfootjon

Differential Revision: D58435760

fbshipit-source-id: cfbb7efba646c5255c9eb62722b0190c272cc340

build/fbcode_builder/manifests/libsodium

@@ -20,7 +20,7 @@ builder = autoconf
 subdir = libsodium-1.0.17
 
 [download.os=windows]
-url = https://download.libsodium.org/libsodium/releases/old/libsodium-1.0.17-msvc.zip
+url = https://download.libsodium.org/libsodium/releases/old/unsupported/libsodium-1.0.17-msvc.zip
 sha256 = f0f32ad8ebd76eee99bb039f843f583f2babca5288a8c26a7261db9694c11467
 
 [build.os=windows]