Adjust codecov test coverage targets

Change from a relative threshold for success (e.g. +/- 1% compared to
previous commit) to an absolute target (e.g. 70% or better coverage).

.codecov.yml

@@ -1,22 +1,20 @@
 # Validate this file:
-#   curl --data-binary @codecov.yml https://codecov.io/validate
-
-# Threshold should not be as high once all packages are being tracked.
+#   curl --data-binary @.codecov.yml https://codecov.io/validate
 
 comment:
   behavior: default
 
 coverage:
   precision: 2
   round: down
-  range: "25...75"
+  range: "50...70"
   status:
     project:
       default:
-        threshold: 1.0%
+        target: 70%
     patch:
       default:
-        threshold: 1.0%
+        target: 70%
 
 ignore:
 - ".github"