This is the mirror image of #2170.

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Add `default_converter` argument to `to_js` and `toJs`. This is the mirror image of #2170.

### Checklists

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     If you think some of these steps are not necessary for your PR,
     just remove those checkboxes, or mark them as checked. Otherwise,
     if some checkboxes are left unmarked, we might assume that your PR
     is not ready to be merged and we might keep you waiting -->

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests
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diff --git a/numpy/linalg/umath_linalg.c.src b/numpy/linalg/umath_linalg.c.src
index 36b99b522..7c2d21189 100644
--- a/numpy/linalg/umath_linalg.c.src
+++ b/numpy/linalg/umath_linalg.c.src
@@ -797,7 +797,6 @@ update_pointers(npy_uint8** bases, ptrdiff_t* offsets, size_t count)
    positives with this warning
 */
 #pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

 /*
  *****************************************************************************

diff --git a/numpy/linalg/umath_linalg.c.src b/numpy/linalg/umath_linalg.c.src
index 36b99b522..7c2d21189 100644
--- a/numpy/linalg/umath_linalg.c.src
+++ b/numpy/linalg/umath_linalg.c.src
@@ -797,7 +797,6 @@ update_pointers(npy_uint8** bases, ptrdiff_t* offsets, size_t count)
    positives with this warning
 */
 #pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

 /*
  *****************************************************************************
