Revert a fix for #101 to fix broken tests relating to PYENV_NATIVE_EXT

test/libexec/pyenv-grep

@@ -1,2 +0,0 @@
-#!/usr/bin/env bash
-grep -E "$@"

test/pyenv_ext.bats

@@ -1,11 +1,3 @@
 #!/usr/bin/env bats
 
 load test_helper
-
-@test "conflicting GREP_OPTIONS" {
-  file="${BATS_TMPDIR}/hello"
-  echo "hello" > "$file"
-  GREP_OPTIONS="-F" run pyenv grep "hell." "$file"
-  assert_success
-  assert_output "hello"
-}