Remove fjson package

.golangci.yml

@@ -26,14 +26,6 @@ linters-settings:
             desc: use `github.com/jackc/pgx/v5` package instead
           - pkg: github.com/jackc/pgx/v4
             desc: use `github.com/jackc/pgx/v5` package instead
-      fjson:
-        # TODO https://github.com/FerretDB/FerretDB/issues/4157
-        files:
-          - $all
-          - "!**/internal/bson/*_test.go"
-          - "!**/internal/util/testutil/*.go"
-        deny:
-          - pkg: github.com/FerretDB/FerretDB/internal/types/fjson
       bson:
         files:
           - $all

CONTRIBUTING.md

@@ -158,8 +158,6 @@ The `internal` subpackages contain most of the FerretDB code:
 
 - `types` package provides Go types matching BSON types that don't have built-in Go equivalents:
   we use `int32` for BSON's int32, but `types.ObjectID` for BSON's ObjectId.
-- `types/fjson` provides converters from/to FJSON for built-in and `types` types.
-  It is used for logging of BSON values and wire protocol messages.
 - `bson` package provides converters from/to BSON for built-in and `types` types.
 - `wire` package provides wire protocol implementation.
 - `clientconn` package provides client connection implementation.