fix mod blacklist update failing if the new version is shorter

Previously `blacklist-update.json` was updated using `File.OpenWrite`, which doesn't truncate before overwriting. If the previous version was longer, that left the longer part at the end of the file.

Author: Pathoschild

docs/release-notes.md

@@ -6,6 +6,7 @@
   * Improved performance.
   * Improved error message when a mod is blocked by Windows Smart App Control.
   * Improved translations. Thanks to To2morrow (updated Korean)!
+  * Fixed rare edge case where a mod blacklist update could fail.
   * Updated internal mod blacklist.
 
 * For mod authors:

src/SMAPI/Framework/SCore.cs

@@ -1840,7 +1840,7 @@ private async Task CheckForUpdatesAsync(IModMetadata[] mods)
 
                 // save new file
                 await using (Stream downloadStream = await newData.AsStream())
-                await using (FileStream stream = File.OpenWrite(Constants.ApiBlacklistFetchedPath))
+                await using (FileStream stream = File.Create(Constants.ApiBlacklistFetchedPath))
                     await downloadStream.CopyToAsync(stream);
 
                 this.Monitor.Log($"   Mod blacklist updated to match the server (updated from {localHash} to {serverHash}). The changes will take effect on the next SMAPI launch.");