Revert "kokoro: Update macos.cfg"

Author: kannanjgithub

buildscripts/kokoro/macos.cfg

@@ -2,7 +2,7 @@
 
 # Location of the continuous shell script in repository.
 build_file: "grpc-java/buildscripts/kokoro/macos.sh"
-timeout_mins: 60
+timeout_mins: 45
 
 # We always build mvn artifacts.
 action {