docs: update for the removal of develop.xml manifest

Since we no longer plan to maintain multiple manifest files for each
branch the relevant part of the documentation needs to explain the new
situation.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

docs/repo-workspace.rst

@@ -33,10 +33,12 @@ The Manifests
 *************
 
 The `manifest repository <https://git.ostc-eu.org/OSTC/OHOS/manifest>`_
-provides the manifests available for configuring a workspace. The project provides two kinds of manifests:
+provides the manifest for configuring a workspace. The project provides
+a single ``default.xml`` manifest file in each of the active branches.
 
-* develop manifests (where some projects are following a branch)
-* default manifests (where all projects are pinned to specific revisions)
+Depending on the specific branch of the manifest repository, that manifest may
+either allow some projects to follow changes by selecting git branches or pin
+all projects to a specific git commit revision.
 
 Setting up the Workspace
 ************************