sagemathgh-38731: Docbuild: Fix conditionalization of documentation o…

…n features

    
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Split out from sagemath#36380.

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URL: sagemath#38731
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee

src/sage_docbuild/builders.py

@@ -1054,7 +1054,7 @@ def get_modules(self, filename):
                 try:
                     tag_name = line[line.index('feature_') + 8:].strip()
                     for feature in all_features():
-                        if tag_name == feature.name.replace('.', '_'):
+                        if tag_name == feature.name.replace('.', '_') and feature.is_present():
                             break
                     else:
                         skip = True