test-update: Drop beta-versions from the base-versions list

No need to keep test coverage for beta-versions anymore given the
presence of official releases.

Change-Id: I039bb6983197ab23c5691ae3678599828ae6c300

Author: MatteoStifano

tests/update/base_versions_current_branch.json

@@ -1,14 +1 @@
-[
-  "2.5.0b1",
-  "2.5.0b2",
-  "2.5.0b3",
-  "2.5.0b4",
-  "2.5.0",
-  "2.5.0p1",
-  "2.5.0p2",
-  "2.5.0p3",
-  "2.5.0p4",
-  "2.5.0p5",
-  "2.5.0p6",
-  "2.5.0p7"
-]
+["2.5.0", "2.5.0p1", "2.5.0p2", "2.5.0p3", "2.5.0p4", "2.5.0p5", "2.5.0p6", "2.5.0p7"]