revert codecov.yml workaround and pin coverage to 4.3.4 (#3662)

* Revert "Attempted workaround for intermittent coverage issues (#3661)"

This reverts commit 84a634c1e7645970382a3a271dfae9ef95685e7a.

* pin coverage to 4.3.4
diff --git a/Jenkinsfile b/Jenkinsfile
index 29f9a76..36cc009 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -238,6 +238,7 @@
                             IF %ERRORLEVEL% NEQ 0 EXIT /B %ERRORLEVEL%
                             virtualenv .codecov
                             call .codecov/Scripts/activate
+                            pip install coverage==4.3.4
                             pip install codecov
                             codecov -e JOB_BASE_NAME,LABEL
                         """
@@ -255,7 +256,7 @@
                                     tox -r --  --color=yes
                                 virtualenv .venv
                                 source .venv/bin/activate
-                                pip install coverage
+                                pip install coverage==4.3.4
                                 bash <(curl -s https://codecov.io/bash) -e JOB_BASE_NAME,LABEL
                             """
                         }
@@ -274,7 +275,7 @@
                                 fi
                                 virtualenv .venv
                                 source .venv/bin/activate
-                                pip install coverage
+                                pip install coverage==4.3.4
                                 bash <(curl -s https://codecov.io/bash) -e JOB_BASE_NAME,LABEL
                             """
                         }