[Security Solution] Consider removing `throttle` from the rule schema

[e40pud]

Post https://github.com/elastic/kibana/pull/154990 updates:

• As part of these changes we realised that we don't really need throttle attribute in rule schema. See comments from @maximpn and @banderror here. We should remove it from here and adjust the rest of the code accordingly.

• We should also remove throttle and notifyWhen from InternalRuleCreate and InternalRuleUpdate rule schema here. See this comment.