Use openjdk instead of oraclejdk in Travis

Might fix the issue with Java 8 builds, error for ref:

Expected feature release number in range of 9 to 14, but got: 8
The command "~/bin/install-jdk.sh --target "/home/travis/oraclejdk8" --workspace "/home/travis/.cache/install-jdk" --feature "8" --license "BCL"" failed and exited with 3 during .

Edit:
Trying to upgrade scalafmt, seems like we're running into the unresolved
issue here: scalameta/scalafmt#1415

.travis.yml

@@ -10,8 +10,8 @@ scala:
    - 2.13.0
 
 jdk:
-  - oraclejdk8
-  - oraclejdk12
+  - openjdk8
+  - openjdk12
 
 env: SJS_TEST_BROWSER=chrome
 
@@ -40,4 +40,4 @@ script:
     coverage
     core/test
 
-after_success: "sbt core/coverageReport core/coveralls"
+after_success: "sbt core/coverageReport core/coveralls"

project/plugins.sbt

@@ -5,7 +5,7 @@ addSbtPlugin("org.scoverage"       % "sbt-scoverage"            % "1.6.0")
 addSbtPlugin("org.scoverage"       % "sbt-coveralls"            % "1.2.7")
 addSbtPlugin("org.foundweekends"   % "sbt-bintray"              % "0.5.5")
 addSbtPlugin("com.github.gseitz"   % "sbt-release"              % "1.0.11")
-addSbtPlugin("org.scalameta"       % "sbt-scalafmt"             % "2.0.4")
+addSbtPlugin("org.scalameta"       % "sbt-scalafmt"             % "2.2.0")
 addSbtPlugin("org.portable-scala"  % "sbt-scalajs-crossproject" % "0.6.1")
 addSbtPlugin("org.scala-js"        % "sbt-scalajs"              % "0.6.28")
 addSbtPlugin("com.lihaoyi"         % "workbench"                % "0.4.1")