Fix missing extension in produced .module file

[mateuszkwiecinski]

Works around gradle/gradle#21526

[github-actions]

Aar size:

Aar size change: +0.0B (210.1KiB -> 210.1KiB)

Diffuse output:

OLD: diffuse-source-file-release
NEW: lazythreetenbp-release.aar

 AAR      │ old       │ new       │ diff 
──────────┼───────────┼───────────┼──────
      jar │  21.2 KiB │  21.2 KiB │  0 B 
 manifest │     249 B │     249 B │  0 B 
    other │      96 B │      96 B │  0 B 
──────────┼───────────┼───────────┼──────
    total │ 162.1 KiB │ 162.1 KiB │  0 B 

 JAR     │ old │ new │ diff      
─────────┼─────┼─────┼───────────
 classes │   6 │   6 │ 0 (+0 -0) 
 methods │  65 │  65 │ 0 (+0 -0) 
  fields │  10 │  10 │ 0 (+0 -0)