Remove POSTGRES_IMAGE environment variable (#11860)

Author: evantahler

build.gradle

@@ -147,7 +147,6 @@ def Task getDockerBuildTask(String artifactName, String projectDir, String build
 
         def buildPlatform = System.getenv('DOCKER_BUILD_PLATFORM') ?: isArm64 ? 'linux/arm64' : 'linux/amd64'
         def alpineImage = System.getenv('ALPINE_IMAGE') ?: isArm64 ? 'arm64v8/alpine:3.14' : 'amd64/alpine:3.14'
-        def postgresImage = System.getenv('POSTGRES_IMAGE') ?: isArm64 ? 'arm64v8/postgres:13-alpine' : 'amd64/postgres:13-alpine'
         def buildArch = System.getenv('DOCKER_BUILD_ARCH') ?: isArm64 ? 'arm64' : 'amd64'
 
         inputDir = file("$projectDir/build/docker")
@@ -156,7 +155,6 @@ def Task getDockerBuildTask(String artifactName, String projectDir, String build
         buildArgs.put('JDK_VERSION', jdkVersion)
         buildArgs.put('DOCKER_BUILD_ARCH', buildArch)
         buildArgs.put('ALPINE_IMAGE', alpineImage)
-        buildArgs.put('POSTGRES_IMAGE', postgresImage)
         buildArgs.put('VERSION', buildVersion)
     })
 }