Revert "Adding a restriction for legal RID values."

This reverts commit 07f3279a730980583403b78c3762c5d246d1d9be.

Reason for revert: Suspect of producing consistent failure in some Chrome trybots, blocking rolls.

Failed test:
external/wpt/webrtc/RTCPeerConnection-addTransceiver.https.html


First failure:
https://ci.chromium.org/p/chromium/builders/try/linux-rel/64597

Original change's description:
> Adding a restriction for legal RID values.
> 
> According to the spec, RID values should be constrained to only
> alpha-numeric values. This was not enforced in our implementation to
> allow for more flexibility.
> It has been brought to our attention that some values that we currently
> consider legal (such as the '~', '=' ';' characters) might cause confusion
> with the simulcast syntax that uses these characters to indicate other
> meanings.
> What's worse, is that some characters, when used in RIDs (such as
> \u{1f937} \u{1f4a9} and \u{1f926}) cause uncontrollable laughter for some
> users which might also be a health hazard.
> This change resolves these issues by restricting RIDs to alpha-numeric.
> 
> Bug: webrtc:10491
> Change-Id: I16e262c87525d0289764beacd098e1525a355463
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132061
> Reviewed-by: Steve Anton <steveanton@webrtc.org>
> Commit-Queue: Amit Hilbuch <amithi@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#27499}

TBR=steveanton@webrtc.org,amithi@webrtc.org

Change-Id: I89f9d8a8d3fa82de8a7d429f11ad7cc30812ba7c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:10491
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132244
Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
Commit-Queue: Guido Urdaneta <guidou@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27525}

pc/sdp_serializer_unittest.cc

@@ -469,10 +469,6 @@ const char* kRidDescriptionMalformedStrings[] = {
     "1 send pt=",
     "1 send pt=abc",
     "1 recv ;;",
-    "~1 recv",
-    "1$2 send",
-    "1=2 send",
-    "1* send",
 };
 
 INSTANTIATE_TEST_SUITE_P(RidDescriptionDeserializationErrors,