vars: Fix test breakage in #130 due to _GO_ROOTDIR

In the previous commit for PR #130, in order to allow plugins to have
their own scoped `_GO_ROOTDIR`, it was necessary to remove its
`readonly` constraint. I'd forgotten to update `tests/vars.bats` to
remove the `-r` flag in the expected output.

Author: mbland

tests/vars.bats

@@ -49,7 +49,7 @@ quotify_expected() {
     "declare -x _GO_KCOV_DIR=\"$_GO_KCOV_DIR\""
     "declare -- _GO_PLUGINS_DIR=\"$TEST_GO_PLUGINS_DIR\""
     'declare -a _GO_PLUGINS_PATHS=()'
-    "declare -rx _GO_ROOTDIR=\"$TEST_GO_ROOTDIR\""
+    "declare -x _GO_ROOTDIR=\"$TEST_GO_ROOTDIR\""
     "declare -rx _GO_SCRIPT=\"$TEST_GO_SCRIPT\""
     "declare -- _GO_SCRIPTS_DIR=\"$TEST_GO_SCRIPTS_DIR\""
     "declare -a _GO_SEARCH_PATHS=(${search_paths[*]})"
@@ -113,7 +113,7 @@ quotify_expected() {
     "declare -x _GO_KCOV_DIR=\"$_GO_KCOV_DIR\""
     "declare -- _GO_PLUGINS_DIR=\"$TEST_GO_PLUGINS_DIR\""
     "declare -a _GO_PLUGINS_PATHS=(${plugins_paths[*]})"
-    "declare -rx _GO_ROOTDIR=\"$TEST_GO_ROOTDIR\""
+    "declare -x _GO_ROOTDIR=\"$TEST_GO_ROOTDIR\""
     "declare -rx _GO_SCRIPT=\"$TEST_GO_SCRIPT\""
     "declare -- _GO_SCRIPTS_DIR=\"$TEST_GO_SCRIPTS_DIR\""
     "declare -a _GO_SEARCH_PATHS=(${search_paths[*]})"