docs: minor comment update for Entity message (#1063)

* docs: minor comment update for Entity message

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proto-google-cloud-datastore-v1/src/main/java/com/google/datastore/v1/Entity.java

@@ -23,9 +23,7 @@
  *
  * <pre>
  * A Datastore data object.
- * An entity is limited to 1 megabyte when stored. That _roughly_
- * corresponds to a limit of 1 megabyte for the serialized form of this
- * message.
+ * Must not exceed 1 MiB - 4 bytes.
  * </pre>
  *
  * Protobuf type {@code google.datastore.v1.Entity}
@@ -447,9 +445,7 @@ protected Builder newBuilderForType(com.google.protobuf.GeneratedMessageV3.Build
    *
    * <pre>
    * A Datastore data object.
-   * An entity is limited to 1 megabyte when stored. That _roughly_
-   * corresponds to a limit of 1 megabyte for the serialized form of this
-   * message.
+   * Must not exceed 1 MiB - 4 bytes.
    * </pre>
    *
    * Protobuf type {@code google.datastore.v1.Entity}

proto-google-cloud-datastore-v1/src/main/proto/google/datastore/v1/entity.proto

@@ -197,9 +197,7 @@ message Value {
 
 // A Datastore data object.
 //
-// An entity is limited to 1 megabyte when stored. That _roughly_
-// corresponds to a limit of 1 megabyte for the serialized form of this
-// message.
+// Must not exceed 1 MiB - 4 bytes.
 message Entity {
   // The entity's key.
   //