[revert] use_default_shell_env = True (#10)

### Description

Originally it was unknown to me that we could use flags to directly disable the stamping of scala imports using 
`build --@io_bazel_rules_scala//scala/settings:stamp_scala_import=False` in the `.bazelrc` file. Discussion in 
 bazelbuild#1232 cleared that up. 

### Motivation

Reverting #8 as it is not needed.

scala/scala_import.bzl

@@ -31,7 +31,6 @@ def _stamp_jar(ctx, jar):
             stamped_file.path,
         ],
         mnemonic = "StampWithIjar",
-        use_default_shell_env = True,
     )
 
     return stamped_file