Fix load-css() specs to allow an empty configuration

These specs were wrong. The proposal clearly indicates that empty
configurations mean a module is not being configured.

Author: nex3

spec/core_functions/meta/load_css/error.hrx

@@ -247,26 +247,6 @@ Error: Built-in module sass:color can't be configured.
 The same file can't be configured multiple times, even if the configuration is
 identical.
 
-<===>
-================================================================================
-<===> with/multi_configuration/double_load/empty/input.scss
-@use "sass:meta";
-
-// An empty `$with` still counts as a configuration.
-@include meta.load-css("other", $with: ());
-@include meta.load-css("other", $with: ());
-
-<===> with/multi_configuration/double_load/empty/_other.scss
-$a: c !default;
-
-<===> with/multi_configuration/double_load/empty/error
-Error: _other.scss was already loaded, so it can't be configured using "with".
-  ,
-5 | @include meta.load-css("other", $with: ());
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-  '
-  input.scss 5:1  root stylesheet
-
 <===>
 ================================================================================
 <===> with/multi_configuration/double_load/both_configured/input.scss
@@ -328,27 +308,6 @@ Error: This module was already loaded, so it can't be configured using "with".
   _midstream.scss 1:1  load-css()
   input.scss 3:1       root stylesheet
 
-<===>
-================================================================================
-<===> with/multi_configuration/use_and_load/empty/input.scss
-@use "sass:meta";
-
-@use "other";
-
-// An empty `$with` still counts as a configuration.
-@include meta.load-css("other", $with: ());
-
-<===> with/multi_configuration/use_and_load/empty/_other.scss
-$a: c !default;
-
-<===> with/multi_configuration/use_and_load/empty/error
-Error: _other.scss was already loaded, so it can't be configured using "with".
-  ,
-6 | @include meta.load-css("other", $with: ());
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-  '
-  input.scss 6:1  root stylesheet
-
 <===>
 ================================================================================
 <===> with/multi_configuration/use_and_load/both_configured/input.scss

spec/core_functions/meta/load_css/with.hrx

@@ -313,3 +313,24 @@ $a: original !default;
 b {
   c: configured;
 }
+
+<===>
+================================================================================
+<===> multi_load/empty/input.scss
+@use "sass:meta";
+@include meta.load-css("upstream", $with: (a: configured));
+
+// An empty configuration map counts as no configuration.
+@include meta.load-css("midstream", $with: ());
+
+<===> multi_load/empty/_midstream.scss
+@use "upstream";
+b {c: upstream.$a}
+
+<===> multi_load/empty/_upstream.scss
+$a: original !default;
+
+<===> multi_load/empty/output.css
+b {
+  c: configured;
+}