Stop requiring non-reversible schemas to be new major versions

[tigrannajaryan]

In schema file definition for rename_attributes transformation we have the following:

When the reverse transformation is not possible it is considered an incompatible change. In this case the MAJOR version number of the schema SHOULD be increased in the new version.

However, at the same time we require that the schema version must be equal to Otel spec version number:

The version number of the schema is the same as the specification version number which publishes the schema.

The combination of these 2 requirements is that any time there is a non-reversible change in rename_attributes section we must increase the major version number of the Otel spec, which obviously is wrong.

I believe we need to delete the requirement that non-reversible rename_attributes transformation requires a new major version number of the schema. We should live with the fact that some changes to semantic conventions are one-way only (from old to new version) and cannot be reversed.

Alternatively (or in addition) we could prohibit any transformations that are non-reversible. This is worth considering too.