Use explicit implementation keywords

https://github.com/david-christiansen/idris-code-highlighter/blob/c9540f049e0cd5895ab21e4e60057bf7efc46864/CONTRIBUTING.md#miscellany

Author: yurrriq

src/Logic.lidr

@@ -1161,7 +1161,7 @@ the value of \idr{b}.
 \todo[inline]{Remove when a release with
 https://github.com/idris-lang/Idris-dev/pull/3925 happens}
 
-> Uninhabited (False = True) where
+> implementation Uninhabited (False = True) where
 >   uninhabited Refl impossible
 
 > restricted_excluded_middle : (p <-> b = True) -> p `Either` Not p

src/Maps.lidr

@@ -88,7 +88,7 @@ about strings:
 \todo[inline]{Remove when a release with
 https://github.com/idris-lang/Idris-dev/pull/3925 happens}
 
-> Uninhabited (False = True) where
+> implementation Uninhabited (False = True) where
 >   uninhabited Refl impossible
 >
 

src/Tactics.lidr

@@ -379,7 +379,7 @@ $\square$
 
 \todo[inline]{Remove if https://github.com/idris-lang/Idris-dev/pull/3925 is merged}
 
-> Uninhabited (False = True) where
+> implementation Uninhabited (False = True) where
 >   uninhabited Refl impossible
 
 \todo[inline]{Edit}