NLS: Update a dead_tilde sequence for bépo 1.0, add one from bépo 1.1

According to https://gitlab.com/bepo/pilotes/-/commits/master/xkb the dead_tilde equals sequence for similareq appears to be based on a beta version of the bépo layout, as it shows up in their commit history prior to the formal version 1.0 release in 2008, but was quickly changed to use dead tilde minus instead by the time the full relase rolled out in 2009. This patch updates this sequence to the one used in the full version since 2009. Additionally, it adds one additional sequence from the 1.1 version of the layout from 2019 to compensate for the loss, which uses the original dead_tilde equals sequence for the useful approxeq symbol.