[Bug] JsonWebToken.ReadToken doesn't correctly check dot 3 in JWE

[pmaytak]

Which version of Microsoft.IdentityModel are you using?
7.4.0

Where is the issue?

• M.IM.JsonWebTokens

Actual behavior
This check incorrectly checks if dot 3 is at the last index (in a malformed JWE). The code still works since JWE in a.b.c. format will be caught when dot 4 is checked.

azure-activedirectory-identitymodel-extensions-for-dotnet/src/Microsoft.IdentityModel.JsonWebTokens/JsonWebToken.cs

Line 466 in fc61f2c

if (Dot3 == encodedTokenSpan.Length) // TODO: Should this be encodedJsonSpan.Length - 1?