Revert "Add reno for Tempest v15.0.0"

We cannot add a new reno into the existing tag, so we need to
revert the patch.

This reverts commit 4e9c1dcf8f5c7f743e4ad98ae9f095b1078a691f.

Change-Id: I7554cdcd7968bde2ce0924dcbac5f349ae230935
diff --git a/releasenotes/notes/15.0.0-start-of-pike-support-4925678d477b0745.yaml b/releasenotes/notes/15.0.0-start-of-pike-support-4925678d477b0745.yaml
deleted file mode 100644
index 5555949..0000000
--- a/releasenotes/notes/15.0.0-start-of-pike-support-4925678d477b0745.yaml
+++ /dev/null
@@ -1,13 +0,0 @@
----
-prelude: >
-    This release is marking the start of Ocata release support in Tempest
-other:
-  - |
-    OpenStack releases supported at this time are **Mitaka**, **Newton**,
-    and **Ocata**.
-
-    The release under current development as of this tag is Pike,
-    meaning that every Tempest commit is also tested against master during
-    the Pike cycle. However, this does not necessarily mean that using
-    Tempest as of this tag will work against a Pike (or future releases)
-    cloud.