lib/*: fix docs to use "returns" instead of "return" (#442388)

lib/modules.nix

@@ -1452,7 +1452,7 @@ let
   };
 
   /**
-    Return a definition with file location information.
+    Returns a definition with file location information.
   */
   mkDefinition = args@{ file, value, ... }: args // { _type = "definition"; };
 
@@ -1541,7 +1541,7 @@ let
     };
 
   /**
-    Return a module that causes a warning to be shown if the
+    Returns a module that causes a warning to be shown if the
     specified option is defined. For example,
 
       mkRemovedOptionModule [ "boot" "loader" "grub" "bootDevice" ] "<replacement instructions>"
@@ -1589,7 +1589,7 @@ let
     };
 
   /**
-    Return a module that causes a warning to be shown if the
+    Returns a module that causes a warning to be shown if the
     specified "from" option is defined; the defined value is however
     forwarded to the "to" option. This can be used to rename options
     while providing backward compatibility. For example,
@@ -1645,7 +1645,7 @@ let
     };
 
   /**
-    Return a module that causes a warning to be shown if any of the "from"
+    Returns a module that causes a warning to be shown if any of the "from"
     option is defined; the defined values can be used in the "mergeFn" to set
     the "to" value.
     This function can be used to merge multiple options into one that has a
@@ -1724,7 +1724,7 @@ let
 
   /**
     Single "from" version of mkMergedOptionModule.
-    Return a module that causes a warning to be shown if the "from" option is
+    Returns a module that causes a warning to be shown if the "from" option is
     defined; the defined value can be used in the "mergeFn" to set the "to"
     value.
     This function can be used to change an option into another that has a
@@ -1822,7 +1822,7 @@ let
   mkDerivedConfig = opt: f: mkOverride (opt.highestPrio or defaultOverridePriority) (f opt.value);
 
   /**
-    Return a module that help declares an option that has been renamed.
+    Returns a module that help declares an option that has been renamed.
     When a value is defined for the old option, it is forwarded to the `to` option.
   */
   doRename =