update flb docker branch version to latest one

Author: zhonghui12

Dockerfile

@@ -3,7 +3,7 @@ FROM public.ecr.aws/amazonlinux/amazonlinux:latest as builder
 # Fluent Bit version; update these for each release
 ENV FLB_VERSION 1.9.6
 # branch to pull parsers from in github.com/fluent/fluent-bit-docker-image
-ENV FLB_DOCKER_BRANCH master
+ENV FLB_DOCKER_BRANCH 1.8
 
 ENV FLB_TARBALL http://github.com/fluent/fluent-bit/archive/v$FLB_VERSION.zip
 RUN mkdir -p /fluent-bit/bin /fluent-bit/etc /fluent-bit/log /tmp/fluent-bit-master/

Dockerfile.debug

@@ -3,7 +3,7 @@ FROM public.ecr.aws/amazonlinux/amazonlinux:latest as builder
 # Fluent Bit version; update these for each release
 ENV FLB_VERSION 1.9.6
 # branch to pull parsers from in github.com/fluent/fluent-bit-docker-image
-ENV FLB_DOCKER_BRANCH master
+ENV FLB_DOCKER_BRANCH 1.8
 
 ENV FLB_TARBALL http://github.com/fluent/fluent-bit/archive/v$FLB_VERSION.zip
 RUN mkdir -p /fluent-bit/bin /fluent-bit/etc /fluent-bit/log /tmp/fluent-bit-master/