[IMP] extensions/custom_admonitions: tweak the HTML structure of dfn

The structure of the `dfn` role is changed from its default
`<em class="dfn">text</em>` to
`<span class="dfn"><span>text</span></span>` to ease the styling.

task-3046383

X-original-commit: 281a893540
Part-of: odoo/documentation#4114

extensions/odoo_theme/translator.py

@@ -10,7 +10,6 @@ from sphinx.writers.html5 import HTML5Translator
 #         └── Odoo Translator
 
 ADMONITION_MAPPING = {
-# The alert classes have been replaced by default BS classes to reduce number of scss lines.
     'note': 'alert-primary',
 
     'tip': 'alert-tip',
@@ -27,7 +26,7 @@ ADMONITION_MAPPING = {
 
     'example': 'alert-success',
     'exercise': 'alert-dark',
-}
+}  # The alert classes have been replaced by default BS classes to reduce number of scss lines.
 
 
 class BootstrapTranslator(HTML5Translator):