massdriver: checksum update for 1.13.6 release

[stefanb]

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Ref:

• found in go 1.26.0, go@1.25 1.25.7 (new formula) #258912
• after recent massdriver 1.13.6 #264939

https://github.com/massdriver-cloud/mass/actions/workflows/release.yaml indicate that tag 1.13.6 was moved

from massdriver-cloud/mass@52adf3d to massdriver-cloud/mass@e244260
Diff: massdriver-cloud/mass@52adf3d...e244260

[github-actions]

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