e2e-tests: Remove unnecessary type specification

As it does not lend a warning in IntelliJ once removed. Indeed, one
"should almost never annotate the type of a private field or a local
variable, as their type will usually be immediately evident in their
value" [1].

[1] https://docs.scala-lang.org/style/types.html#inference

Change-Id: I02ead66bf8524d56028a0e654e2e23796675e5fe