Have instanbul-lib-cov use caret for semver in package.json (#747)

Author: jennifer-shehane

package.json

@@ -57,7 +57,7 @@
     "debug": "4.3.4",
     "execa": "4.1.0",
     "globby": "11.1.0",
-    "istanbul-lib-coverage": "3.0.0",
+    "istanbul-lib-coverage": "^3.0.0",
     "js-yaml": "4.1.0",
     "nyc": "15.1.0"
   },