Skip deleted file when updating release version in comments

(cherry picked from commit a71caa28e7)
Signed-off-by: Hadrien Croubois <hadrien.croubois@gmail.com>

scripts/release/update-comment.js

@@ -22,7 +22,7 @@ const [ tag ] = run('git', 'tag')
 // Ordering tag → HEAD is important here.
 const files = run('git', 'diff', tag, 'HEAD', '--name-only', 'contracts/**/*.sol')
   .split(/\r?\n/)
-  .filter(file => file && !file.match(/mock/i));
+  .filter(file => file && !file.match(/mock/i) && fs.existsSync(file));
 
 for (const file of files) {
   const current = fs.readFileSync(file, 'utf8');