ES-1978: corrected syntax in CODEOWNERS file (#236)

* `.ci/*` only catches files directly in `.ci` folder, any subfolders
are not affected
* `/.ci/` correctly sets ownership of all files in that folder to
Infrastructure and Release team
* same for `.gradle` folder
* `/.github` to be owned by Infra & Release, but CODEOWNERS file still are with Rest

.github/CODEOWNERS

@@ -1,7 +1,9 @@
 * @corda/rest
-# Build scripts should be audited by BLT
-*.gradle           @corda/infrastructure-release
-gradle.properties  @corda/corda5-team-leads
-Jenkinsfile        @corda/infrastructure-release
-.ci/*              @corda/infrastructure-release
-gradle/*           @corda/infrastructure-release
+# Build scripts should be audited by Infrastructure & Release team
+*.gradle            @corda/infrastructure-release
+gradle.properties   @corda/corda5-team-leads
+Jenkinsfile         @corda/infrastructure-release
+/.ci/               @corda/infrastructure-release
+/.github/           @corda/infrastructure-release
+/.github/CODEOWNERS @corda/rest # keep CODEOWNERS owned by the Rest team
+/gradle/            @corda/infrastructure-release