Revert "update bazelci.py to use new docker images (#1899)"

This reverts commit fbd7163f28796155f3ca73491642d209a63abb91.
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 24fa625..a4a0ee8 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -417,10 +417,10 @@
 # working directory.
 PLATFORMS = {
     "centos7": {
-        "name": "CentOS 7",
-        "emoji-name": ":centos: 7",
+        "name": "CentOS 7 (OpenJDK 8, gcc 4.8.5)",
+        "emoji-name": ":centos: 7 (OpenJDK 8, gcc 4.8.5)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/centos7",
+        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/centos7-java8",
         "python": "python3.6",
     },
     "centos7_java11": {
@@ -465,20 +465,13 @@
         "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu1804-java11",
         "python": "python3.6",
     },
-    "ubuntu2004_java11": {
+    "ubuntu2004": {
         "name": "Ubuntu 20.04 LTS (OpenJDK 11, gcc 9.4.0)",
         "emoji-name": ":ubuntu: 20.04 LTS (OpenJDK 11, gcc 9.4.0)",
         "publish_binary": [],
         "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2004-java11",
         "python": "python3.8",
     },
-    "ubuntu2004": {
-        "name": "Ubuntu 20.04 LTS",
-        "emoji-name": ":ubuntu: 20.04 LTS",
-        "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2004",
-        "python": "python3.8",
-    },
     "ubuntu2004_arm64": {
         "name": "Ubuntu 20.04 LTS ARM64 (OpenJDK 11, gcc 9.4.0)",
         "emoji-name": ":ubuntu: 20.04 LTS ARM64 (OpenJDK 11, gcc 9.4.0)",
@@ -496,20 +489,13 @@
         "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2004-java11-kythe",
         "python": "python3.8",
     },
-    "ubuntu2204_java17": {
+    "ubuntu2204": {
         "name": "Ubuntu 22.04 (OpenJDK 17, gcc 11.2.0)",
         "emoji-name": ":ubuntu: 22.04 (OpenJDK 17, gcc 11.2.0)",
         "publish_binary": [],
         "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2204-java17",
         "python": "python3",
     },
-    "ubuntu2204": {
-        "name": "Ubuntu 22.04",
-        "emoji-name": ":ubuntu: 22.04",
-        "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2204",
-        "python": "python3",
-    },
     "fedora39": {
         "name": "Fedora 39 (OpenJDK 17, gcc 13.1.1)",
         "emoji-name": ":fedora: 39 (OpenJDK 17, gcc 13.1.1)",