Update maven.yml to fix codecov bindings (#1664)

.github/workflows/maven.yml

@@ -24,3 +24,5 @@ jobs:
         cache: maven
     - name: Build with Maven
       run: mvn -B package --file pom.xml
+    - uses: codecov/codecov-action@v2      
+      # https://github.com/codecov/codecov-action

README.md

@@ -1,10 +1,9 @@
 Anserini
 ========
-![build](https://github.com/castorini/anserini/actions/workflows/maven.yml/badge.svg)
+[![build](https://github.com/castorini/anserini/actions/workflows/maven.yml/badge.svg)](https://github.com/castorini/anserini/actions)
 [![codecov](https://codecov.io/gh/castorini/anserini/branch/master/graph/badge.svg)](https://codecov.io/gh/castorini/anserini)
 [![Generic badge](https://img.shields.io/badge/Lucene-v8.3.0-brightgreen.svg)](https://archive.apache.org/dist/lucene/java/8.3.0/)
 [![Maven Central](https://img.shields.io/maven-central/v/io.anserini/anserini?color=brightgreen)](https://search.maven.org/search?q=a:anserini)
-[![PyPI](https://img.shields.io/pypi/v/pyserini?color=brightgreen)](https://pypi.org/project/pyserini/)
 [![LICENSE](https://img.shields.io/badge/license-Apache-blue.svg?style=flat)](https://www.apache.org/licenses/LICENSE-2.0)
 [![doi](http://img.shields.io/badge/doi-10.1145%2F3239571-blue.svg?style=flat)](https://doi.org/10.1145/3239571)