[Devtools] Change Lighthouse throttling text to "Slow 4G".
[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/+/1575823
Reviewed-by: Erik Luo <26192f5e05d23e5ee959014fb911d780e566545b@chromium.org>
Reviewed-by: Paul Irish <5f672bbedd2fccb2b3e838838e74ef989148de66@chromium.org>
Commit-Queue: Paul Irish <5f672bbedd2fccb2b3e838838e74ef989148de66@chromium.org>
Commit-Queue: Connor Clark <2d5c837a0b2cf015b24acdf5e50262e50d986795@google.com>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#652602}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 33c7ee83367a4b488d8024ac040d6f0a942db6ab
ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend