update configuration files for release-drafter

.github/release-drafter-dev-6.1.x.yml

@@ -0,0 +1,7 @@
+_extends: growi:.github/release-drafter.yml
+
+prerelease: true
+
+# Filter previous releases to consider only those with the tags starts with 'v6.1'
+include-pre-releases: true
+tag-prefix: v6.1

.github/release-drafter-dev-7.0.x.yml

@@ -2,6 +2,6 @@ _extends: growi:.github/release-drafter.yml
 
 prerelease: true
 
-# Filter previous releases to consider only those with the tags starts with 'v6.2'
+# Filter previous releases to consider only those with the tags starts with 'v7.0'
 include-pre-releases: true
 tag-prefix: v7.0