Bump prometheus-client-mmap to 0.9.8

This fixes a critical error where a nil exception would be hit
if an error occurred while logging a Prometheus metric:

https://gitlab.com/gitlab-org/prometheus-client-mmap/merge_requests/36

1 files changed, 1 insertions, 1 deletions

diff --git a/Gemfile b/Gemfile
index f65549f2734..f567eac3ee0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -309,7 +309,7 @@ group :metrics do
   gem 'influxdb', '~> 0.2', require: false
 
   # Prometheus
-  gem 'prometheus-client-mmap', '~> 0.9.7'
+  gem 'prometheus-client-mmap', '~> 0.9.8'
   gem 'raindrops', '~> 0.18'
 end