jira - fixed base64 decode bug (#2349)

* fixed base64 decode bug

* added changelog fragment

changelogs/fragments/2349-jira-bugfix-b64decode.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - jira - fixed error when loading base64-encoded content as attachment (https://github.com/ansible-collections/community.general/pull/2349).

plugins/modules/web_infrastructure/jira.py

@@ -596,7 +596,7 @@ def _prepare_attachment(filename, content=None, mime_type=None):
             content = f.read()
     else:
         try:
-            content = base64.decode(content)
+            content = base64.b64decode(content)
         except binascii.Error as e:
             raise Exception("Unable to base64 decode file content: %s" % e)