cc dynamic_config: rm legacy Snapshot::Get

* Removed legacy `dynamic_config::Snapshot::Get` method, use `operator[]` instead.
commit_hash:ae91207cf6be7b7235db672918d323aac7e6a143

Author: Anton3

core/include/userver/dynamic_config/snapshot.hpp

@@ -151,16 +151,6 @@ class Snapshot final {
     template <typename VariableType>
     const VariableType& operator[](const Key<VariableType>&) &&;
 
-    /// @cond
-    // No longer supported, use `config[key]` instead
-    template <typename T>
-    const T& Get() const& USERVER_IMPL_LIFETIME_BOUND;
-
-    // No longer supported, use `config[key]` instead
-    template <typename T>
-    const T& Get() &&;
-    /// @endcond
-
 private:
     // for the constructor
     friend class Source;
@@ -292,16 +282,6 @@ const VariableType& Snapshot::operator[](const Key<VariableType>&) && {
     static_assert(!sizeof(VariableType), "keep the Snapshot before using, please");
 }
 
-template <typename T>
-const T& Snapshot::Get() const& USERVER_IMPL_LIFETIME_BOUND {
-    return (*this)[T::kDeprecatedKey];
-}
-
-template <typename T>
-const T& Snapshot::Get() && {
-    static_assert(!sizeof(T), "keep the Snapshot before using, please");
-}
-
 }  // namespace dynamic_config
 
 USERVER_NAMESPACE_END

core/src/dynamic_config/config_test.cpp

@@ -120,21 +120,6 @@ UTEST_F(DynamicConfigTest, VariableSnapshotPtr) {
 
 UTEST_F(DynamicConfigTest, Copy) { EXPECT_EQ(source_.GetCopy(kIntConfig), 5); }
 
-struct OldConfig final {
-    static const dynamic_config::Key<OldConfig> kDeprecatedKey;
-
-    int foo{42};
-};
-
-const dynamic_config::Key<OldConfig> OldConfig::kDeprecatedKey{dynamic_config::ConstantConfig{}, OldConfig{}};
-
-UTEST(DynamicConfig, TheOldWay) {
-    const dynamic_config::StorageMock storage{{OldConfig::kDeprecatedKey, {}}};
-
-    const auto config = storage.GetSource().GetSnapshot();
-    EXPECT_EQ(config.Get<OldConfig>().foo, 42);
-}
-
 class DummyClient final {
 public:
     explicit DummyClient(dynamic_config::Source config)