Update comment on alternate builds in .travis.yml

rust-lang#45810 (comment)

Author: SimonSapin

.travis.yml

@@ -18,10 +18,9 @@ matrix:
     - env: IMAGE=dist-x86_64-linux DEPLOY=1
       if: branch = auto
 
-    # "alternate" deployments, these are "nightlies" but don't have assertions
-    # turned on, they're deployed to a different location primarily for projects
-    # which are stuck on nightly and don't want llvm assertions in the artifacts
-    # that they use.
+    # "alternate" deployments, these are "nightlies" but have LLVM assertions
+    # turned on, they're deployed to a different location primarily for
+    # additional testing.
     - env: IMAGE=dist-x86_64-linux DEPLOY_ALT=1
       if: branch = try OR branch = auto