Travis-CI: remove cache workaround from scala#335

Author: SethTisue

Diff for: .travis.yml

@@ -11,9 +11,9 @@ scala:
   - 2.13.4
 
 env:
-  - ADOPTOPENJDK=8     SCALAJS_VERSION=       CACHE_WORKAROUND=see-PR-335
-  - ADOPTOPENJDK=8     SCALAJS_VERSION=1.3.1  CACHE_WORKAROUND=see-PR-335
-  - ADOPTOPENJDK=11    SCALAJS_VERSION=       CACHE_WORKAROUND=see-PR-335
+  - ADOPTOPENJDK=8     SCALAJS_VERSION=
+  - ADOPTOPENJDK=8     SCALAJS_VERSION=1.3.1
+  - ADOPTOPENJDK=11    SCALAJS_VERSION=
 
 matrix:
   include: