Move the list of Base64 digits out of the test data

This is part of the definition of the encoding, not a choice of test
parameter, so keep it with the test code.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/suites/test_suite_base64.data b/tests/suites/test_suite_base64.data
index 1f94c54..5556668 100644
--- a/tests/suites/test_suite_base64.data
+++ b/tests/suites/test_suite_base64.data
@@ -23,10 +23,10 @@
 mask_of_range:65:90
 
 enc_char (all digits)
-enc_chars:"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+enc_chars:
 
 dec_value (all characters)
-dec_chars:"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+dec_chars:
 
 Test case mbedtls_base64_encode #1 buffer just right
 mbedtls_base64_encode:"":"":0:0