[dv, doc] Replace all 'dv.plan' with testplan

This commit purges all instances of "DV plan" to make the documentation
nomenclature as described in our DV methodology consistent.

what we capture in the HJSon -> testplan
what we capture in the markdown doc -> DV document

Signed-off-by: Srikrishna Iyer <sriyer@google.com>
diff --git a/util/dashboard/dashboard_validate.py b/util/dashboard/dashboard_validate.py
index 487e4b9..df4f9dd 100644
--- a/util/dashboard/dashboard_validate.py
+++ b/util/dashboard/dashboard_validate.py
@@ -36,7 +36,7 @@
 field_optional = {
     'design_spec':
     ['s', "path to the design specification, relative to repo root"],
-    'dv_doc': ['s', "path to the DV plan, relative to repo root"],
+    'dv_doc': ['s', "path to the DV document, relative to repo root"],
     'hw_checklist': ['s', "path to the hw_checklist, relative to repo root"],
     'sw_checklist': ['s', "path to the sw_checklist, relative to repo root"],
     'design_stage': ['s', "design stage of module"],