Remove legacy JSON reader and concurrent_unordered_map.cuh. (#15813)

This completes the final two steps and closes #15537. Also addresses one step of #12261.

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - Kyle Edwards (https://github.com/KyleFromNVIDIA)
  - David Wendt (https://github.com/davidwendt)
  - Shruti Shivakumar (https://github.com/shrshi)
  - Matthew Roeschke (https://github.com/mroeschke)

URL: #15813

cpp/CMakeLists.txt

@@ -390,8 +390,6 @@ add_library(
   src/io/json/json_tree.cu
   src/io/json/nested_json_gpu.cu
   src/io/json/read_json.cu
-  src/io/json/legacy/json_gpu.cu
-  src/io/json/legacy/reader_impl.cu
   src/io/json/parser_features.cpp
   src/io/json/write_json.cu
   src/io/orc/aggregate_orc_metadata.cpp

cpp/include/cudf/io/json.hpp

@@ -270,15 +270,6 @@ class json_reader_options {
    */
   bool is_enabled_dayfirst() const { return _dayfirst; }
 
-  /**
-   * @brief Whether the legacy reader should be used.
-   *
-   * @deprecated Since 24.06
-   *
-   * @returns true if the legacy reader will be used, false otherwise
-   */
-  [[deprecated]] bool is_enabled_legacy() const { return _legacy; }
-
   /**
    * @brief Whether the reader should keep quotes of string values.
    *
@@ -406,15 +397,6 @@ class json_reader_options {
    */
   void enable_dayfirst(bool val) { _dayfirst = val; }
 
-  /**
-   * @brief Set whether to use the legacy reader.
-   *
-   * @deprecated Since 24.06
-   *
-   * @param val Boolean value to enable/disable the legacy reader
-   */
-  [[deprecated]] void enable_legacy(bool val) { _legacy = val; }
-
   /**
    * @brief Set whether the reader should keep quotes of string values.
    *
@@ -605,20 +587,6 @@ class json_reader_options_builder {
     return *this;
   }
 
-  /**
-   * @brief Set whether to use the legacy reader.
-   *
-   * @deprecated Since 24.06
-   *
-   * @param val Boolean value to enable/disable legacy parsing
-   * @return this for chaining
-   */
-  [[deprecated]] json_reader_options_builder& legacy(bool val)
-  {
-    options._legacy = val;
-    return *this;
-  }
-
   /**
    * @brief Set whether the reader should keep quotes of string values.
    *

cpp/src/groupby/hash/groupby.cu

@@ -16,7 +16,6 @@
 
 #include "groupby/common/utils.hpp"
 #include "groupby/hash/groupby_kernels.cuh"
-#include "hash/concurrent_unordered_map.cuh"
 
 #include <cudf/aggregation.hpp>
 #include <cudf/column/column.hpp>