get back "electron-mail" executable name

* Executable name change "electron-mail => ElectronMail" in v5.3.1 got caused by electron-userland/electron-builder#9068.

Author: vladimiry

electron-builder.yml

@@ -1,6 +1,7 @@
 appId: 'github.com/vladimiry/ElectronMail'
 artifactName: ${name}-${version}-${os}-${arch}.${ext}
 productName: 'ElectronMail'
+executableName: 'electron-mail'
 publish: null
 forceCodeSigning: false