Revert "base64Decode: clearer error message when an invalid character…

… is detected"

We have a safer way of doing this.

This reverts commit dc3ccf0.

src/libutil/util.cc

@@ -243,9 +243,8 @@ std::string base64Decode(std::string_view s)
         if (c == '\n') continue;
 
         char digit = base64DecodeChars[(unsigned char) c];
-        if (digit == npos) {
-            throw Error("invalid character in Base64 string: '%c' in '%s'", c, s.data());
-        }
+        if (digit == npos)
+            throw Error("invalid character in Base64 string: '%c'", c);
 
         bits += 6;
         d = d << 6 | digit;