Delete .coveralls.yml (#19782)

This was added for https://github.com/lemurheavy/coveralls-public/issues/1103 but that didn't help.
diff --git a/.coveralls.yml b/.coveralls.yml
deleted file mode 100644
index cf27a37..0000000
--- a/.coveralls.yml
+++ /dev/null
@@ -1 +0,0 @@
-service_name: travis-pro