Deactivate CSS overrides

Table column alignment was fixed with bootstraph-theme update.
No need for css override nor extra css file.

This partially reverts commit bc33092.

Author: pavoljuhas

_static/diffpy-styles.css

@@ -1,5 +1 @@
-/* Restore left-aligned table columns for sphinx 2.0 and later */
-
-table.align-default {
-    text-align: left;
-}
+/* Add CSS style overrides here */

conf.py

@@ -361,5 +361,6 @@ def apply(self):
 
 def setup(app):
     app.add_transform(MakeAbsoluteURIsRelative)
-    app.add_css_file('diffpy-styles.css')
+    ## uncomment in case we need style overrides
+    #app.add_css_file('diffpy-styles.css')
     return