repository: Remove `#set_config()` implementation

There are no callers anymore which use `#set_config()` to write to the
repository's gitconfig, and the RPC which implements this has been
deprecated with no replacement by Gitaly. We can thus remove this
function as well as its underlying implementation in the
RepositoryService.

lib/gitlab/git/repository.rb

@@ -907,12 +907,6 @@ module Gitlab
         gitaly_repository_client.set_full_path(full_path)
       end
 
-      def set_config(entries)
-        wrapped_gitaly_errors do
-          gitaly_repository_client.set_config(entries)
-        end
-      end
-
       def disconnect_alternates
         wrapped_gitaly_errors do
           gitaly_repository_client.disconnect_alternates

lib/gitlab/gitaly_client/repository_service.rb

@@ -281,25 +281,6 @@ module Gitlab
         nil
       end
 
-      def set_config(entries)
-        return if entries.empty?
-
-        request = Gitaly::SetConfigRequest.new(repository: @gitaly_repo)
-        entries.each do |key, value|
-          request.entries << build_set_config_entry(key, value)
-        end
-
-        GitalyClient.call(
-          @storage,
-          :repository_service,
-          :set_config,
-          request,
-          timeout: GitalyClient.fast_timeout
-        )
-
-        nil
-      end
-
       def license_short_name
         request = Gitaly::FindLicenseRequest.new(repository: @gitaly_repo)
 

spec/lib/gitlab/git/repository_spec.rb

@@ -1749,29 +1749,6 @@ RSpec.describe Gitlab::Git::Repository, :seed_helper do
     end
   end
 
-  describe '#set_config' do
-    let(:repository) { mutable_repository }
-    let(:entries) do
-      {
-        'test.foo1' => 'bla bla',
-        'test.foo2' => 1234,
-        'test.foo3' => true
-      }
-    end
-
-    it 'can set config settings' do
-      expect(repository.set_config(entries)).to be_nil
-
-      expect(repository_rugged.config['test.foo1']).to eq('bla bla')
-      expect(repository_rugged.config['test.foo2']).to eq('1234')
-      expect(repository_rugged.config['test.foo3']).to eq('true')
-    end
-
-    after do
-      entries.keys.each { |k| repository_rugged.config.delete(k) }
-    end
-  end
-
   describe '#merge_to_ref' do
     let(:repository) { mutable_repository }
     let(:branch_head) { '6d394385cf567f80a8fd85055db1ab4c5295806f' }