alias Nullable.get this: improve deprecation grammar, fix documentation

std/typecons.d

@@ -2960,7 +2960,6 @@ Params:
 Gets the value if not null. If `this` is in the null state, and the optional
 parameter `fallback` was provided, it will be returned. Without `fallback`,
 calling `get` with a null state is invalid.
-This function is also called for the implicit conversion to `T`.
 
 Params:
     fallback = the value to return in case the `Nullable` is null.
@@ -2982,7 +2981,7 @@ Returns:
     }
 
 ///
-deprecated
+deprecated("Implicit conversion with `alias Nullable.get this` is deprecated. Please use `.get` explicitly.")
 @system unittest
 {
     import core.exception : AssertError;
@@ -3000,7 +2999,7 @@ deprecated
     assert(i == 5);
 }
 
-    deprecated("Deprecated to rely on implicit Nullable.get. Please use .get explicitly instead.")
+    deprecated("Implicit conversion with `alias Nullable.get this` is deprecated. Please use `.get` explicitly.")
     @property ref inout(T) get_() inout @safe pure nothrow
     {
         enum message = "Called `get' on null Nullable!" ~ T.stringof ~ ".";
@@ -3024,6 +3023,7 @@ deprecated
 /**
 Implicitly converts to `T`.
 `this` must not be in the null state.
+This feature is deprecated.
  */
     alias get_ this;
 }
@@ -3080,7 +3080,7 @@ auto nullable(T)(T t)
     assertThrown!Throwable(a.get);
 }
 
-deprecated("Deprecated to rely on implicit Nullable.get. Please use .get explicitly instead.")
+deprecated("Implicit conversion with `alias Nullable.get this` is deprecated. Please use `.get` explicitly.")
 @system unittest
 {
     import std.exception : assertThrown;