travis: drop beta Rust target

I don't think we've ever seen a build failure on this test target so it seems like a waste of resources to continuously build it.
mgeisler · Sep 11, 2019 · 2c51bfc · 2c51bfc
1 parent eff1d0d
commit 2c51bfc
Showing 1 changed file with 1 addition and 2 deletions.
diff --git a/.travis.yml b/.travis.yml
@@ -1,9 +1,8 @@
 language: rust
 
 rust:
-  - 1.31.0
+  - 1.31.0 # Rust 2018
   - stable
-  - beta
   - nightly
 
 cache: cargo