Fixed typo in changelog

Author: fbricon

CHANGELOG.md

@@ -8,7 +8,7 @@
  * Completion doesn't use file cache for included XML schema. See [lsp4xml#570](https://github.com/angelozerr/lsp4xml/pull/570)
  * Prevent from NPE validation with schemaLocaton and "schema.reference.4" error. See [lsp4xml#569](https://github.com/angelozerr/lsp4xml/pull/569)
 
-### Performances
+### Performance
 
  * Improve performance and memory for validation by caching XML Schema / DTD. See [lsp4xml#534](https://github.com/angelozerr/lsp4xml/issues/534)
 
@@ -268,4 +268,4 @@
 * File association should support relative path for systemId. See [#142](https://github.com/angelozerr/lsp4xml/issues/142).
 * Code completion is sometimes "one off". See [#80](https://github.com/redhat-developer/vscode-xml/issues/80).
 * DTD validation problems not refreshing correctly. See [#79](https://github.com/redhat-developer/vscode-xml/issues/79).
-* No validation when referencing a schema in the same directory. See [#144](https://github.com/angelozerr/lsp4xml/issues/144)
+* No validation when referencing a schema in the same directory. See [#144](https://github.com/angelozerr/lsp4xml/issues/144)