fix typo

src/frontend/src/pages/Chapters/Camel/ChapterLambda/course.md

@@ -117,7 +117,7 @@ ligo dry-run lambda.mligo main 'ChangeFunc(fun (c : coordinates) -> {x=c.x*100;y
 
 ## Your mission
 
-We have a smart contract that references planets is the Sol system. Since the beginning of the project, all celestial bodies were considered as planets.
+We have a smart contract that registers planets of the Sol system. Since the beginning of the project, all celestial bodies were considered as planets.
 Since 2006, the IAU decided that celetial bodies with a mass under 100 are not considered as a planet but as a dwarf-planet. Hopefully we forecasted this kind of change! A _DeduceCategoryChange_ entrypoint allows us to change the lambda which determines the category of a celestial body. All we have to do is define the new rule and all registered celestial bodies will be updated.
 
 Take a look at the starmap contract in the editor tabs.

src/frontend/src/pages/Chapters/Pascal/ChapterLambda/course.md

@@ -110,7 +110,7 @@ ligo dry-run lambda.ligo main 'ChangeFunc(function (const c : coordinates) : coo
 
 ## Your mission
 
-We have a smart contract that reference planets is the Sol system. Since the beginning of the project, all celestial bodies were considered as planets.
+We have a smart contract that registers planets of the Sol system. Since the beginning of the project, all celestial bodies were considered as planets.
 Since 2006, the IAU decided that celetial bodies with a mass under 100 are not considered as a planet but as a dwarf-planet. Hopefully we forecasted this kind of change! A _DeduceCategoryChange_ entrypoint allows us to change the lambda which determines the category of a celestial body. All we have to do is define the new rule and all registered celestial bodies will be updated.
 
 Take a look at the starmap contract in the editor tabs.

src/frontend/src/pages/Chapters/Reason/ChapterLambda/course.md

@@ -110,7 +110,7 @@ ligo dry-run lambda.religo main 'ChangeFunc((c : coordinates) : coordinates => {
 
 ## Your mission
 
-We have a smart contract that reference planets is the Sol system. Since the beginning of the project, all celestial bodies were considered as planets.
+We have a smart contract that registers planets of the Sol system. Since the beginning of the project, all celestial bodies were considered as planets.
 Since 2006, the IAU decided that celetial bodies with a mass under 100 are not considered as a planet but as a dwarf-planet. Hopefully we forecasted this kind of change! A _DeduceCategoryChange_ entrypoint allows us to change the lambda which determines the category of a celestial body. All we have to do is define the new rule and all registered celestial bodies will be updated.
 
 Take a look at the starmap contract in the editor tabs.