[Devtools] Change Lighthouse throttling text to "Slow 4G".

For terminology alignment with CruX.

Bug: https://github.com/googlechrome/lighthouse/pull/6163

Change-Id: I90ebd73384947114f9b237f4afee3fdd4683db15
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1575823Reviewed-by: Erik Luo <luoe@chromium.org>
Reviewed-by: Paul Irish <paulirish@chromium.org>
Commit-Queue: Paul Irish <paulirish@chromium.org>
Commit-Queue: Connor Clark <cjamcl@google.com>
Cr-Commit-Position: refs/heads/master@{#652602}

third_party/blink/renderer/devtools/front_end/audits2/Audits2Controller.js

@@ -260,12 +260,12 @@ Audits2.RuntimeSettings = [
     },
     options: [
       {
-        label: ls`Simulated Fast 3G, 4x CPU Slowdown`,
+        label: ls`Simulated Slow 4G, 4x CPU Slowdown`,
         value: 'default',
         title: 'Throttling is simulated, resulting in faster audit runs with similar measurement accuracy'
       },
       {
-        label: ls`Applied Fast 3G, 4x CPU Slowdown`,
+        label: ls`Applied Slow 4G, 4x CPU Slowdown`,
         value: 'devtools',
         title: 'Typical DevTools throttling, with actual traffic shaping and CPU slowdown applied'
       },