CI: travis-ci: upgrade LibreSSL versions

3.0.2 --> 3.1.1
2.9.2 --> 3.0.2
2.8.3 --> 2.9.2
diff --git a/.travis.yml b/.travis.yml
index 08a8992..ea71686 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -74,16 +74,16 @@
   - os: linux
     if: type == push
     compiler: clang
-    env: TARGET=linux-glibc LIBRESSL_VERSION=3.0.2 CC=clang-9
+    env: TARGET=linux-glibc LIBRESSL_VERSION=3.1.1 CC=clang-9
   - os: linux
     env: DEBUG_OPTIONS=""
     if: type == cron
     compiler: clang
-    env: TARGET=linux-glibc LIBRESSL_VERSION=2.9.2 CC=clang-9
+    env: TARGET=linux-glibc LIBRESSL_VERSION=3.0.2 CC=clang-9
   - os: linux
     if: type == cron
     compiler: clang
-    env: TARGET=linux-glibc LIBRESSL_VERSION=2.8.3 EXTRA_OBJS="contrib/prometheus-exporter/service-prometheus.o" CC=clang-9
+    env: TARGET=linux-glibc LIBRESSL_VERSION=2.9.2 EXTRA_OBJS="contrib/prometheus-exporter/service-prometheus.o" CC=clang-9
   - os: linux
     if: type == cron
     compiler: clang