[blinkpy] Remove 'mac10.13_retina-blink-rel' from builders.json

This builder was removed in
https://chromium-review.googlesource.com/c/chromium/src/+/2317705, but
the builders.json config, which blinkpy's BuildersList class relies on,
was seemingly overlooked. That broke the WPT importer (and any other use
of BuildersList).

Bug: 1112063, 1104846
Change-Id: I9d08cdde6992fd14147eedbd42ad38187c11b6ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2333747Reviewed-by: Erik Staab <estaab@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794183}

third_party/blink/tools/blinkpy/common/config/builders.json

@@ -101,12 +101,6 @@
         "specifiers": ["Mac10.13", "Release"],
         "is_try_builder": true
     },
-    "mac10.13_retina-blink-rel": {
-        "master": "tryserver.blink",
-        "port_name": "mac-retina",
-        "specifiers": ["Retina", "Release"],
-        "is_try_builder": true
-    },
     "mac10.14-blink-rel": {
         "master": "tryserver.blink",
         "port_name": "mac-mac10.14",