Remove deprecated scenario img_dir option

It's time to remove deprecated CONF.scenario.img_dir which got
deprecated in the 25.0.0 tag.

Change-Id: I86ad219265a67a1c016e8efe04677993a0437ede
Closes-Bug: #1393881
diff --git a/releasenotes/notes/Remove-deprecated-scenario.img_dir-option-da626e6153181e16.yaml b/releasenotes/notes/Remove-deprecated-scenario.img_dir-option-da626e6153181e16.yaml
new file mode 100644
index 0000000..2514e48
--- /dev/null
+++ b/releasenotes/notes/Remove-deprecated-scenario.img_dir-option-da626e6153181e16.yaml
@@ -0,0 +1,8 @@
+---
+upgrade:
+  - |
+    img_dir scenario option has been deprecated and it's being removed.
+    Starting Tempest 25.0.0 release, CONF.scenario.img_file needs a full path
+    for the image. Until this release, old behavior was maintained and kept
+    working however a user needs to specify the full path in
+    CONF.scenario.img_file config option from now on.