Also remove linux-rel-intermittent

Judged unnecessary: https://github.com/servo/servo/pull/23633#issuecomment-505576450

etc/ci/buildbot_steps.yml

@@ -5,18 +5,6 @@ env:
   SCCACHE_IDLE_TIMEOUT: "1200"
   GST_DEBUG: '3'
 
-linux-rel-intermittent:
- env:
-   CC: clang-4.0
-   CXX: clang++-4.0
- commands:
-  - ./mach clean-nightlies --keep 3 --force
-  - ./mach clean-cargo-cache --keep 3 --force
-  - ./etc/ci/clean_build_artifacts.sh
-  - ./mach build --release -p servo
-  - ./etc/ci/check_intermittents.sh --log-raw intermittents.log
-  - ./etc/ci/clean_build_artifacts.sh
-
 linux-rel-nogate:
  env:
    CC: clang-4.0
@@ -91,3 +79,4 @@ linux-nightly: []
 arm32: []
 arm64: []
 mac-rel-intermittent: []
+linux-rel-intermittent: []

etc/ci/check_intermittents.sh

@@ -1,22 +0,0 @@
-#!/usr/bin/env bash
-
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at https://mozilla.org/MPL/2.0/.
-
-set -o errexit
-set -o nounset
-set -o pipefail
-REPEAT_COUNT=100
-
-while read test_name; do
-    echo "  - Checking ${test_name}"
-    ./mach test-wpt \
-        --release \
-        --log-raw - \
-        --repeat "${REPEAT_COUNT}" \
-        "${test_name}" \
-        > intermittents.log \
-        < /dev/null
-done < "etc/ci/former_intermittents_wpt.txt"
-

etc/ci/former_intermittents_css.txt

@@ -1,4 +0,0 @@
-/css-flexbox-1_dev/html/flexbox-basic-iframe-vert-001.htm
-/css-transforms-1_dev/html/transform-table-007.htm
-/css-transforms-1_dev/html/transform-abspos-002.htm
-/css-transforms-1_dev/html/transform-abspos-007.htm

etc/ci/former_intermittents_wpt.txt

@@ -1,2 +0,0 @@
-/_mozilla/css/canvas_over_area.html
-/_mozilla/css/iframe/hide_layers2.html