Revert "fix (startup): fix font theme key (opensearch-project#6703) (o…

…pensearch-project#6707)"

This reverts commit 3c78162.

src/legacy/ui/ui_render/bootstrap/startup.js.hbs

@@ -36,6 +36,8 @@ var themeVersion = rawThemeVersion === 'v7' ? 'v7' : 'v8';
 
 window.__osdThemeTag__ = themeVersion + darkMode;
 
+var themeSourceKey = themeVersion === 'v7' ? 'v7' : 'default';
+
 var themeSources = {{THEME_SOURCES}};
 
 var themeDefinition = themeSources[themeVersion][darkMode];
@@ -80,8 +82,8 @@ document.head.insertBefore(themedStylesDom, stylesheetTarget);
 var fontTexts = {{fontText}};
 var fontCodes = {{fontCode}};
 
-var fontText = fontTexts[themeVersion];
-var fontCode = fontCodes[themeVersion];
+var fontText = fontTexts[themeSourceKey];
+var fontCode = fontCodes[themeSourceKey];
 
 var fontTarget = document.querySelector('head meta[name="add-fonts-here"]');