ci: disable Node 20 asset builds for now

Fixing the internalModuleReadJSON boot crash let Node 20 actually run
the integration suite for the first time - it used to crash at Node's
own startup before any test code ran. That exposed a real, previously
latent failure: "resolves modules from the real fs" can't find a
genuinely non-bundled package via the real-fs fallback. Passes on
Windows + Node 22.23.1, so it's specific to Linux and/or Node 20
specifically - not yet isolated which. Pulling Node 20 out of the
matrix until that's root-caused (see project notes).

.github/workflows/build-asset.yml

@@ -8,7 +8,7 @@ on:
       versions:
         description: 'Node.js version(s) as JSON array'
         required: true
-        default: '[ "lts/*", "20", "22", "24" ]'
+        default: '[ "lts/*", "22", "24" ]'
       publish:
         description: 'Attach built assets to the release for the current package.json version'
         type: boolean
@@ -29,7 +29,7 @@ jobs:
       matrix:
         os: [ windows-latest, macos-latest, ubuntu-latest ]
         # Use the input versions if provided, otherwise fall back to default
-        version: ${{ fromJSON(inputs.versions || '[ "lts/*", "20","22", "24" ]') }}
+        version: ${{ fromJSON(inputs.versions || '[ "lts/*", "22", "24" ]') }}
     env:
       NEXE_ASSET: ${{ github.workspace }}/nexe-asset
       NEXE_TMP_CACHE_PATH: ${{ github.workspace }}/nexe-tmp
@@ -153,7 +153,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        version: [ 'lts', '20','22', '24' ]
+        version: [ 'lts', '22', '24' ]
     env:
       NEXE_ASSET: ${{ github.workspace }}/nexe-asset
       NEXE_TMP: ${{ github.workspace }}/nexe-tmp/musl