Add missing AUDI_A3_MK3 transmission & SRS f/w (#25328)

* Add missing AUDI_A3_MK3 trans & SRS f/w + cleanup

@Lord_Veit#2600 Audi A3 E-Tron (EU)  DongleID/route 7a66a72837a92935|2022-08-01--20-08-22
https://discord.com/channels/469524606043160576/524592892627517450/1003759334796316752

Cleanup was simply replacing `\0` w/ `\x`... a problem I noticed while adding missing firmware.

* Add missing AUDI_A3_MK3 trans & SRS f/w

Reverted previous "cleanup"... which was actually more of a disaster.

selfdrive/car/volkswagen/values.py

@@ -685,6 +685,7 @@ FW_VERSIONS = {
       b'\xf1\x870D9300013B \xf1\x894931',
       b'\xf1\x870D9300041N \xf1\x894512',
       b'\xf1\x870D9300043T \xf1\x899699',
+      b'\xf1\x870DD300046  \xf1\x891604',
       b'\xf1\x870DD300046A \xf1\x891602',
       b'\xf1\x870DD300046F \xf1\x891602',
       b'\xf1\x870DD300046G \xf1\x891601',
@@ -695,6 +696,7 @@ FW_VERSIONS = {
     (Ecu.srs, 0x715, None): [
       b'\xf1\x875Q0959655AB\xf1\x890388\xf1\x82\0211111001111111206110412111321139114',
       b'\xf1\x875Q0959655AM\xf1\x890315\xf1\x82\x1311111111111111311411011231129321212100',
+      b'\xf1\x875Q0959655AM\xf1\x890318\xf1\x82\x1311111111111112311411011531159321212100',
       b'\xf1\x875Q0959655BJ\xf1\x890339\xf1\x82\x1311110011131100311111011731179321342100',
       b'\xf1\x875Q0959655J \xf1\x890825\xf1\x82\023111112111111--171115141112221291163221',
       b'\xf1\x875Q0959655J \xf1\x890830\xf1\x82\023121111111211--261117141112231291163221',