(DOCSP-49855) Removes EOL brances from backportrc.json. (#1103)

Author: erabil-mdb

.backportrc.json

@@ -2,7 +2,7 @@
     "repoOwner": "mongodb",
     "repoName": "docs-atlas-cli",
 
-    "targetBranchChoices": ["v1.41", "v1.40", "v1.39", "v1.38", "v1.37", "v1.36", "v1.35", "v1.34", "v1.33", "v1.32", "v1.31", "v1.30", "v1.29", "v1.28", "v1.27", "v1.26", "v1.25", "v1.24", "v1.23", "v1.22", "v1.21", "v1.20", "v1.19", "v1.18", "v1.17", "v1.16", "v1.15", "v1.14", "v1.13", "v1.12"],
+    "targetBranchChoices": ["v1.41", "v1.40", "v1.39", "v1.38", "v1.37"],
 
     "editor": "code",