Use ubuntu-20.04 runner for Linux releases

Author: marc0der

.github/workflows/release.yml

@@ -69,7 +69,7 @@ jobs:
           - { target: aarch64-apple-darwin     , os: macos-latest  ,                  jreleaser_platform: osx-aarch_64   }
           - { target: x86_64-apple-darwin      , os: macos-latest  ,                  jreleaser_platform: osx-x86_64     }
           - { target: x86_64-pc-windows-msvc   , os: windows-latest,                  jreleaser_platform: windows-x86_64 }
-          - { target: x86_64-unknown-linux-gnu , os: self-hosted   ,                  jreleaser_platform: linux-x86_64   }
+          - { target: x86_64-unknown-linux-gnu , os: ubuntu-20.04  ,                  jreleaser_platform: linux-x86_64   }
           - { target: aarch64-unknown-linux-gnu, os: ubuntu-20.04  , use-cross: true, jreleaser_platform: linux-aarch_64 }
     runs-on: ${{ matrix.job.os }}
     steps: