Fix coverage flow

Author: sxwei123

.github/workflows/coverage.yml

@@ -1,9 +1,6 @@
 name: "Coverage"
 
 on:
-  push:
-    branches:
-      - master
   pull_request:
     branches:
       - master

README.md

@@ -1,6 +1,6 @@
 # quick-stable-stringify
 
-![Test status](https://github.com/sxwei123/quick-stable-stringify/workflows/Coverage/badge.svg?branch=master)
+![Test status](https://github.com/sxwei123/quick-stable-stringify/workflows/Coverage/badge.svg)
 
 Deterministic `JSON.stringify()` - a faster version of [@epoberezkin](https://github.com/epoberezkin)'s [fast-json-stable-strigify](https://github.com/epoberezkin/fast-json-stable-stringify). Built with Typescript and modern Javascript.