[DOCS] Fixes in Plugin API articles for 24.3 (#26134)

Port: #26129

* Removed unused toctree.
* Added explanation of Microseconds (JIRA: 149717)

Co-authored-by: Karol Blaszczak <karol.blaszczak@intel.com>

Author: msmykx-intel

docs/articles_en/documentation/openvino-extensibility/openvino-plugin-library/advanced-guides/quantized-models.rst

@@ -1,13 +1,6 @@
-.. {#openvino_docs_ov_plugin_dg_quantized_models}
-
 Quantized models compute and restrictions
 =========================================
 
-.. toctree::
-   :maxdepth: 1
-   :hidden:
-
-
 .. meta::
    :description: Learn about the support for quantized models with different
                  precisions and the FakeQuantize operation used to express

docs/articles_en/documentation/openvino-extensibility/openvino-plugin-library/plugin-api-references.rst

@@ -1,5 +1,3 @@
-.. {#openvino_docs_ie_plugin_api_references}
-
 Plugin API Reference
 ====================
 

src/inference/dev_api/openvino/runtime/exec_model_info.hpp

@@ -44,7 +44,7 @@ static const char OUTPUT_PRECISIONS[] = "outputPrecisions";
 
 /**
  * @ingroup ov_dev_exec_model
- * @brief Used to get a value of execution time of the executable primitive.
+ * @brief Used to get a value of execution time of the executable primitive, where Mcs = Microseconds.
  */
 static const char PERF_COUNTER[] = "execTimeMcs";