Drop building wheel for python 3.4 (#6406)

https://github.com/matthew-brett/multibuild/pull/240

kokoro/release/python/linux/build_artifacts.sh

diff --git a/kokoro/release/python/linux/build_artifacts.sh b/kokoro/release/python/linux/build_artifacts.sh
index c2806b7..5f9eaa1 100755
--- a/kokoro/release/python/linux/build_artifacts.sh
+++ b/kokoro/release/python/linux/build_artifacts.sh
@@ -50,7 +50,6 @@
 }
 
 build_artifact_version 2.7
-build_artifact_version 3.4
 build_artifact_version 3.5
 build_artifact_version 3.6
 build_artifact_version 3.7

kokoro/release/python/macos/build_artifacts.sh

diff --git a/kokoro/release/python/macos/build_artifacts.sh b/kokoro/release/python/macos/build_artifacts.sh
index 02d666f..148d1f9 100755
--- a/kokoro/release/python/macos/build_artifacts.sh
+++ b/kokoro/release/python/macos/build_artifacts.sh
@@ -51,7 +51,6 @@
 }
 
 build_artifact_version 2.7
-build_artifact_version 3.4
 build_artifact_version 3.5
 build_artifact_version 3.6
 build_artifact_version 3.7