fix: remove explicit arch arrays from Linux targets to prevent cross-arch package contamination

Fixes #116 - electron-builder was building both x64 and arm64 packages on each
runner regardless of CLI flags, causing the ARM64 runner's amd64.deb (with ARM
binaries inside) to overwrite the correct x64 package during artifact deduplication.

package.json

@@ -144,27 +144,9 @@
     },
     "linux": {
       "target": [
-        {
-          "target": "AppImage",
-          "arch": [
-            "x64",
-            "arm64"
-          ]
-        },
-        {
-          "target": "deb",
-          "arch": [
-            "x64",
-            "arm64"
-          ]
-        },
-        {
-          "target": "rpm",
-          "arch": [
-            "x64",
-            "arm64"
-          ]
-        }
+        "AppImage",
+        "deb",
+        "rpm"
       ],
       "category": "Development",
       "icon": "build/icon.png",