move note regarding testing for erroneous inputs to introduction.md

... because it applies to the exercise in general, not a particular approach.

Author: petrem

exercises/practice/rna-transcription/.approaches/dictionary-join/content.md

@@ -39,11 +39,6 @@ def to_rna(dna_strand):
 For a relatively small number of elements, using lists is fine and may be faster, but as the number of elements increases, the memory consumption increases and performance decreases.
 You can read more about [when to choose generators over list comprehensions][list-comprehension-choose-generator-expression] to dig deeper into the topic.
 
-
-~~~~exercism/note
-As of this writing, no invalid DNA characters are in the argument to `to_rna()`, so there is no error handling required for invalid input.
-~~~~
-
 [dictionaries]: https://docs.python.org/3/tutorial/datastructures.html?#dictionaries
 [const]: https://realpython.com/python-constants/
 [join]: https://docs.python.org/3/library/stdtypes.html?#str.join

exercises/practice/rna-transcription/.approaches/introduction.md

@@ -41,6 +41,11 @@ For more information, check the [dictionary look-up with `join()` approach][appr
 If performance matters, consider using the [`translate()` with `maketrans()` approach][approach-translate-maketrans].
 How an implementation behaves in terms of performance may depend on the actual data being processed, on hardware, and other factors.
 
+
+~~~~exercism/note
+As of this writing, no invalid DNA characters are in the argument to `to_rna()`, so there is no error handling required for invalid input.
+~~~~
+
 [Unicode]: https://en.wikipedia.org/wiki/Unicode
 [approach-translate-maketrans]: https://exercism.org/tracks/python/exercises/rna-transcription/approaches/translate-maketrans
 [approach-dictionary-join]: https://exercism.org/tracks/python/exercises/rna-transcription/approaches/dictionary-join

exercises/practice/rna-transcription/.approaches/translate-maketrans/content.md

@@ -26,11 +26,6 @@ In the `to_rna()` function, the [`translate()`][translate] method is called on t
 and is passed the translation table.
 The output of `translate()` is a string where all of the input DNA characters have been replaced by their RNA complement in the translation table.
 
-
-~~~~exercism/note
-As of this writing, no invalid DNA characters are in the argument to `to_rna()`, so there is no error handling required for invalid input.
-~~~~
-
 [dictionaries]: https://docs.python.org/3/tutorial/datastructures.html?#dictionaries
 [maketrans]: https://docs.python.org/3/library/stdtypes.html?#str.maketrans
 [const]: https://realpython.com/python-constants/