Fix codespell issues (#1320)

.codespellrc

@@ -1,3 +1,3 @@
 [codespell]
 skip = .git,.mypy_cache,build,testdata
-ignore-words-list = fpr,claus,feld,nd,bu,ue,te,fo,afile,manuel
+ignore-words-list = fpr,claus,feld,nd,bu,ue,te,fo,afile,manuel,checkin,assertIn,rin

CODE_OF_CONDUCT.md

@@ -6,7 +6,7 @@ In the interest of fostering an open and welcoming environment, we as
 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
+level of experience, education, socioeconomic status, nationality, personal
 appearance, race, religion, or sexual identity and orientation.
 
 ## Our Standards