build: build stable and beta channels with MV3

Manifest Version 2 will be deprecated in June 2024 in Chrome. This CL
switches the build system to release the beta and stable Chrome builds
with a MV3 build instead of a MV2 one.

It also removes the |web-ext lint| check in the lint job because
Chrome's MV3 builds are quite different from Firefox's MV3 builds (which
the extension doesn't provide) and this makes the |web-ext lint| check
fail. The lint job now only checks that the extension can be built.

Fixed: translateselectedtext:4
Change-Id: I2e0645aa1eac73b9e8bc7e7a551a625497127722
diff --git a/tools/release.bash b/tools/release.bash
index d5f634d..dbe6d39 100644
--- a/tools/release.bash
+++ b/tools/release.bash
@@ -16,7 +16,6 @@
                    "stable" or "canary". Defaults to "stable".
     -b, --browser  indicates the target browser for the release. Can be
                    "chromium", "chromium_mv3, "edge" or "edge_mv3".
-                   Defaults to "chromium".
     -f, --fast     indicates that the release shouldn't generate the
                    i18n credits JSON file.
 
@@ -33,7 +32,7 @@
 eval set -- "$opts"
 
 channel=stable
-browser=chromium
+browser=
 fast=0
 
 while true; do