Fix sample .bazelrc for RBE.
Fix sample .bazelrc for RBE.

Removes a '↳' character that shouldn't have been included and uses a leading '_' for the personal config name as recommended by the Bazel guide[1].

[1] https://docs.bazel.build/versions/3.4.0/guide.html#--config

Bug: 160254092
Change-Id: I646915d05efff3048569121215b03373b3cecf20

world-federation-of-advertisers/cross-media-measurement,world-federation-of-advertisers/cross-media-measurement,world-federation-of-advertisers/cross-media-measurement