Remove escapes from code blocks

[guardrex]

Looks like escapes were applied within code blocks on the migration. Those escapes should be reverted.

Example from docs/framework/configure-apps/file-schema/windows-identity-foundation/claimsauthenticationmanager.md:

```
\<system.identityModel>
\<identityConfiguration name="MyIdentity">
<claimsAuthenticationManager type="MyNamespace.CustomClaimsAuthenticationManager, MyAssembly"/>
</identityConfiguration>
\</microsoft.identityModel>
```

Thanks @svick for reporting in https://github.com/dotnet/docs/pull/2147/files#r116362786.