chore: add .backportrc to gitignore (#26403)

diff --git a/.gitignore b/.gitignore
index 63c51c4..89f5626 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,3 +16,4 @@
 .idea/
 .vscode/
 node_modules/
+.backportrc.json
\ No newline at end of file