Add .no_warn to the evaluation of `require_batched_execution_for_cu…

…stom_microbatch_strategy`

The situation in which we want to warn the user about the behavior flag is
exceedingly small. Specifically, we want to fire a deprecation warning when
1. The behavior flag is false
2. The user is executing a `microbatch` model
3. The user has a custome `microbatch` macro

In dbt-adapters we could check (1) and (2), but we have no ability to
check (3). Thus emitting the warning in dbt-adapters upon evaluation of
the behavior flag `require_batched_execution_for_custom_microbatch_strategy`
is _undesirable_. Instead we'll be emitting a deprecation warning from
dbt-core.

dbt/adapters/base/impl.py

@@ -1579,7 +1579,7 @@ def valid_incremental_strategies(self):
 
     def builtin_incremental_strategies(self):
         builtin_strategies = ["append", "delete+insert", "merge", "insert_overwrite"]
-        if self.behavior.require_batched_execution_for_custom_microbatch_strategy:
+        if self.behavior.require_batched_execution_for_custom_microbatch_strategy.no_warn:
             builtin_strategies.append("microbatch")
 
         return builtin_strategies