Update manifest for launcher v1.2.1

Author: Christopher Liu

data/org.sugarlabs.MusicBlocks.yaml

@@ -42,23 +42,23 @@ modules:
         branch: 'HEAD'
       - type: file
         dest-filename: MusicBlocks.AppImage
-        url: https://github.com/sugarlabs/musicblocks-launcher/releases/download/continuous/MusicBlocks-3.5.1-arm64.AppImage
-        sha256: 40e35c6b3ce230fcf18f70919bc33db2b4fadd9b4fcb21ed8c9a9fd1291b06a0
+        url: https://github.com/sugarlabs/musicblocks-launcher/releases/download/v1.2.1/MusicBlocks-3.5.1-arm64.AppImage
+        sha256: 3cca8ad13eb88b976918540857b771350bec36e43e9551df6454bf690cbd131b
         size: 140783237
         only-arches:
           - aarch64
       - type: file
         dest-filename: MusicBlocks.AppImage
-        url: https://github.com/sugarlabs/musicblocks-launcher/releases/download/continuous/MusicBlocks-3.5.1-armv7l.AppImage
-        sha256: b12ee8f0083c673523b76a37893f76543efe5aa543f1c4c69a72711cf398c467
-        size: 125620259
+        url: https://github.com/sugarlabs/musicblocks-launcher/releases/download/v1.2.1/MusicBlocks-3.5.1-armv7l.AppImage
+        sha256: 19fbea50cd4a641d4a2af1eb7e99a640d04187cb740ad43761e640fa974c8198
+        size: 125620262
         only-arches:
           - arm
       - type: file
         dest-filename: MusicBlocks.AppImage
-        url: https://github.com/sugarlabs/musicblocks-launcher/releases/download/continuous/MusicBlocks-3.5.1-x86_64.AppImage
-        sha256: 55fcc4fd61c278d41caddded502ed5ff3bf867386e5ae382d0b793611fca7ea5
-        size: 134913872
+        url: https://github.com/sugarlabs/musicblocks-launcher/releases/download/v1.2.1/MusicBlocks-3.5.1-x86_64.AppImage
+        sha256: 6b385ea53d55396b906f3604ede256ae520f018ef2393631669d7e95fafaa92f
+        size: 134913869
         only-arches:
           - x86_64
 
@@ -70,4 +70,4 @@ modules:
       - type: script
         dest-filename: musicblocks-run
         commands:
-          - exec /app/bin/musicblocks/musicblocks "$@" --no-sandbox
+          - exec /app/bin/musicblocks/musicblocks-launcher "$@" --no-sandbox