[ci skip] [skip ci] Fix dev label in README.md

Author: isuruf

README.md

@@ -25,7 +25,7 @@ See License section for information about wheels
 
 optionally, you may choose to install an early [developer preview](https://github.com/symengine/python-symengine-feedstock):
 
-    conda install python-symengine -c symengine/dev -c conda-forge
+    conda install python-symengine -c symengine/label/dev -c conda-forge
 
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