DOC: Fix typo. [skip ci]

Author: Taher Chegini

CODE_OF_CONDUCT.rst

@@ -9,7 +9,7 @@ contributors and maintainers pledge to making participation in our
 project and our community a harassment-free experience for everyone,
 regardless of age, body size, disability, ethnicity, sex
 characteristics, gender identity and expression, level of experience,
-education, socio-economic status, nationality, personal appearance,
+education, socioeconomic status, nationality, personal appearance,
 race, religion, or sexual identity and orientation.
 
 Our Standards