fix: Clarify error message.

Author: chriseppstein

Diff for: packages/@css-blocks/core/src/BlockParser/features/composes-block.ts

@@ -41,7 +41,7 @@ export async function composeBlock(configuration: Configuration, root: postcss.R
 
         for (let sel of parsedSel) {
           if (sel.selector.next) {
-            block.addError(new errors.InvalidBlockSyntax(`Style composition is not allowed in rule sets with a scope selector.`, sourceRange(configuration, root, sourceFile, decl)));
+            block.addError(new errors.InvalidBlockSyntax(`Style composition is not allowed in rule sets with a context selector.`, sourceRange(configuration, root, sourceFile, decl)));
           }
           let foundStyles = getStyleTargets(block, sel.selector);
           for (let blockClass of foundStyles.blockClasses) {

Diff for: packages/@css-blocks/core/test/BlockParser/block-composition-test.ts

@@ -87,7 +87,7 @@ export class BlockNames extends BEMProcessor {
     return assertMultipleErrorsRejection(
       [{
       type: InvalidBlockSyntax,
-      message: `Style composition is not allowed in rule sets with a scope selector. (foo/bar/test-block.css:2:44)`}],
+      message: `Style composition is not allowed in rule sets with a context selector. (foo/bar/test-block.css:2:44)`}],
       this.process(filename, inputCSS, {importer: imports.importer()}));
   }