INSTALL: fixing copy-paste bugs.

Thanks to Tobias (@Tobias on Gitlab) for noticing.

INSTALL.in

@@ -382,13 +382,13 @@ These are:
      Python plug-ins, you can use -Dpython=false.
 
   -Djavascript=false  If for some reason you don't want to install the
-     Python plug-ins, you can use -Djavascript=false.
+     JavaScript plug-ins, you can use -Djavascript=false.
 
   -Dlua=false  If for some reason you don't want to install the
-     Python plug-ins, you can use -Dlua=false.
+     Lua plug-ins, you can use -Dlua=false.
 
   -Dvala-plugins=disabled  If for some reason you don't want to install the
-     Python plug-ins, you can use -Dvala-plugins=disabled.
+     Vala plug-ins, you can use -Dvala-plugins=disabled.
 
 
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