[1.8] remove _assets_def argument on build_op_context (dagster-io#23172)

## Summary & Motivation

## How I Tested These Changes

python_modules/dagster/dagster/_core/execution/context/invocation.py

@@ -56,7 +56,6 @@
 from dagster._core.types.dagster_type import DagsterType
 from dagster._utils.forked_pdb import ForkedPdb
 from dagster._utils.merger import merge_dicts
-from dagster._utils.warnings import deprecation_warning
 
 from .compute import AssetExecutionContext, OpExecutionContext
 from .system import StepExecutionContext, TypeCheckContext
@@ -858,7 +857,6 @@ def build_op_context(
  partition_key: Optional[str] = None,
  partition_key_range: Optional[PartitionKeyRange] = None,
  mapping_key: Optional[str] = None,
- _assets_def: Optional[AssetsDefinition] = None,
 ) -> DirectOpExecutionContext:
  """Builds op execution context from provided parameters.
 
@@ -878,8 +876,6 @@ def build_op_context(
  output. Can be accessed using ``context.get_mapping_key()``.
  partition_key (Optional[str]): String value representing partition key to execute with.
  partition_key_range (Optional[PartitionKeyRange]): Partition key range to execute with.
- _assets_def (Optional[AssetsDefinition]): Internal argument that populates the op's assets
- definition, not meant to be populated by users.
 
  Examples:
  .. code-block:: python
@@ -896,16 +892,6 @@ def build_op_context(
  "legacy version, ``config``. Please provide one or the other."
  )
 
- if _assets_def:
- deprecation_warning(
- subject="build_op_context",
- additional_warn_text=(
- "Parameter '_assets_def' was passed to build_op_context. This parameter was intended for internal use only, and has been deprecated "
- ),
- breaking_version="1.8.0",
- stacklevel=1,
- )
-
  op_config = op_config if op_config else config
  return DirectOpExecutionContext(
  resources_dict=check.opt_mapping_param(resources, "resources", key_type=str),