Get rid of Travis CI badge in README (#652)

Co-authored-by: Alexey Alexandrov <aalexand@users.noreply.github.com>
diff --git a/README.md b/README.md
index bc2b3cc..05f9095 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,4 @@
 [![Github Action CI](https://github.com/google/pprof/workflows/ci/badge.svg)](https://github.com/google/pprof/actions)
-[![Travis CI](https://travis-ci.org/google/pprof.svg?branch=master)](https://travis-ci.org/google/pprof)
 [![Codecov](https://codecov.io/gh/google/pprof/graph/badge.svg)](https://codecov.io/gh/google/pprof)
 
 # Introduction