Bug 1720188 - Update suite version for comm-central->comm-beta merge. r=justdave

Updating the suite version for the c-c to c-b merge is a simple substitution
operation in both files. The "version-files" cannot be used for suite as
there is no support in mozilla-version for Seamonkey's versions.

Depends on D121669, D121668 (version-control-tools)

Test Plan:
https://treeherder.mozilla.org/jobs?repo=try-comm-central&revision=ae6f9cce64c5cbc6a272eda34c302bad028e717b

The push fails for some odd reason (try allows new remote heads so why did it fail?), but the diffs are correct!

Differential Revision: https://phabricator.services.mozilla.com/D121670

taskcluster/ci/config.yml

@@ -99,6 +99,12 @@ merge-automation:
                 - - .gecko_rev.yml
                   - "GECKO_HEAD_REPOSITORY: https://hg.mozilla.org/mozilla-central"
                   - "GECKO_HEAD_REPOSITORY: https://hg.mozilla.org/releases/mozilla-beta"
+                - - suite/config/version.txt
+                  - a1
+                  - ''
+                - - suite/config/version_display.txt
+                  - a1
+                  - b1
             merge-old-head: true
             base-tag: 'BETA_{major_version}_BASE'
             end-tag: 'BETA_{major_version}_END'