Bump rewriter from 7fc7ef5 to 16ae768 (#2341)

Pulls in mit-plv/rewriter's adaptation to the removal of the
deprecated coq-core.* findlib library aliases
(rocq-prover/rocq#21955), merged as
mit-plv/rewriter#203.

Without this, the dev (rocq dev / 9.3) docker CI builds fail while
compiling the rewriter submodule with:

    *** Error: In file src/Rewriter/Util/plugins/RewriterBuild.v
    findlib error: coq-core.plugins.ltac not found
    ...
    required by `coq-rewriter.rewriter_build'

because the rewriter META still required coq-core.plugins.* which no
longer exists on rocq 9.3. The bumped rewriter generates the META
per Coq version (coq-core.* on 8.x/9.0-9.2, rocq-runtime.* on 9.3).

https://claude.ai/code/session_01PjCbMk9zjAZWvZHuznFXqh

Co-authored-by: Claude <noreply@anthropic.com>

Author: JasonGross