fix(build): quote-safe changelog line for v1.0.0.13

"Fix a possible hang: ..." has ": " inside a plain YAML scalar, which
PyYAML reads as a mapping key, so update_manifest.py failed in CI.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

build.yaml

@@ -16,7 +16,7 @@ changelog:
     client; VP9/AV1 often needed a CPU transcode) and uses Jellyfin's own
     ffmpeg for the merge
   - If yt-dlp fails, the built-in downloader is tried instead
-  - Fix a possible hang: yt-dlp's output is now read while it runs, so a
+  - Fix a possible hang. yt-dlp's output is now read while it runs, so a
     full output buffer can no longer block it
 
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