Revert "Add support for negative requirements"

This reverts commit b2068e80a814e5cf5c5d3786ea15747483bb236f.

This change does not appear to do the correct thing with "any" and
caused issues for us in production.  Our gate requirement of
jenkins>=+1 _and_ workflow=+1 became jenkins >=+1 or workflow=+1.

Change-Id: Ie5aa776b2dd718fcf025148073a0171332f358fb
diff --git a/tests/fixtures/layout-requirement-older-than.yaml b/tests/fixtures/layout-requirement-older-than.yaml
index 0e011cc..2edf9df 100644
--- a/tests/fixtures/layout-requirement-older-than.yaml
+++ b/tests/fixtures/layout-requirement-older-than.yaml
@@ -2,7 +2,7 @@
   - name: pipeline
     manager: IndependentPipelineManager
     require:
-      any-approval:
+      approval:
         - username: jenkins
           older-than: 48h
     trigger:
@@ -20,7 +20,7 @@
     trigger:
       gerrit:
         - event: comment-added
-          require-any-approval:
+          require-approval:
             - username: jenkins
               older-than: 48h
     success: