Reconfigure codecov to reduce false alarm rate.

codecov.yml

 codecov:
-  require_ci_to_pass: true
-
-comment:
-    behavior: default
-    branches:
-        - "master"
+  require_ci_to_pass: yes
 
 coverage:
+  precision: 2
+  round: down
+  range: "70...100"
   status:
     project:
       default:
+        # basic
         target: auto
-        threshold: 0%
-
+        threshold: 1%
+        base: auto
     patch:
       default:
+        # basic
         target: 100%
+        threshold: 1%
+        base: auto
+
+comment:
+  layout: "reach, diff, flags, files"
+  behavior: default
+  require_changes: false  # if true: only post the comment if coverage changes
+  require_base: no        # [yes :: must have a base report to post]
+  require_head: yes       # [yes :: must have a head report to post]
+  branches: null          # branch names that can post comment