AZP: fix matrix (ansible-collections#876) (ansible-collections#877)

Co-authored-by: Andrew Klychkov <aklychko@redhat.com>

Author: patchback[bot]

.azure-pipelines/azure-pipelines.yml

@@ -244,7 +244,6 @@ stages:
       - Docker_2_19
       - Docker_2_18
       - Docker_2_17
-      - Docker_2_15
       - Remote_devel
       - Remote_2_19
       - Remote_2_18

README.md

@@ -101,7 +101,6 @@ Even if they are present in our test matrix now, they can be removed at any mome
 ## Tested with ansible-core
 
 Tested with the following `ansible-core` releases:
-- 2.15 (only integration on Fedora 37)
 - 2.16
 - 2.17
 - 2.18