Revert "Bump v15.0.0-nightly.20210609"

This reverts commit c9ccd136a8170199d3f7c64b9adc745e119cffbb.

ELECTRON_VERSION

@@ -1 +1 @@
-15.0.0-nightly.20210609
+15.0.0-nightly.20210608

package.json

@@ -1,6 +1,6 @@
 {
   "name": "electron",
-  "version": "15.0.0-nightly.20210609",
+  "version": "15.0.0-nightly.20210608",
   "repository": "https://github.com/electron/electron",
   "description": "Build cross platform desktop apps with JavaScript, HTML, and CSS",
   "devDependencies": {

shell/browser/resources/win/electron.rc

@@ -50,8 +50,8 @@ END
 //
 
 VS_VERSION_INFO VERSIONINFO
- FILEVERSION 15,0,0,20210609
- PRODUCTVERSION 15,0,0,20210609
+ FILEVERSION 15,0,0,20210608
+ PRODUCTVERSION 15,0,0,20210608
  FILEFLAGSMASK 0x3fL
 #ifdef _DEBUG
  FILEFLAGS 0x1L