gh-35752: Clarification on the MAX_MODULUS of float matrices modulo `n`
    
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### 📚 Description

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Improves the documentation to give more precisions on the upper limit
MAX_MODULUS of `matrix_modn_dense_float.pyx` for performances sake.
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URL: #35752
Reported by: Marie Bonboire
Reviewer(s): Vincent Neiger

Author: Release Manager

src/sage/matrix/matrix_modn_dense_double.pyx

@@ -51,8 +51,9 @@ cdef class Matrix_modn_dense_double(Matrix_modn_dense_template):
 
     These are matrices with integer entries mod ``n`` represented as
     floating-point numbers in a 64-bit word for use with LinBox routines.
-    This allows for ``n`` up to `2^{23}`.  The analogous
-    ``Matrix_modn_dense_float`` class is used for smaller moduli.
+    This allows for ``n`` up to `2^{23}`. By default, the analogous
+    ``Matrix_modn_dense_float`` class is used for smaller moduli, specifically
+    for ``n`` up to `2^{8}`.
 
     Routines here are for the most basic access, see the
     ``matrix_modn_dense_template.pxi`` file for higher-level routines.

src/sage/matrix/matrix_modn_dense_float.pyx

@@ -3,7 +3,7 @@
 # distutils: library_dirs = CBLAS_LIBDIR
 # distutils: include_dirs = CBLAS_INCDIR
 r"""
-Dense matrices over `\ZZ/n\ZZ` for `n < 2^{11}` using LinBox's ``Modular<float>``
+Dense matrices over `\ZZ/n\ZZ` for `n < 2^{8}` using LinBox's ``Modular<float>``
 
 AUTHORS:
 - Burcin Erocal
@@ -44,12 +44,13 @@ include "matrix_modn_dense_template.pxi"
 
 cdef class Matrix_modn_dense_float(Matrix_modn_dense_template):
     r"""
-    Dense matrices over `\ZZ/n\ZZ` for `n < 2^{11}` using LinBox's ``Modular<float>``
+    Dense matrices over `\ZZ/n\ZZ` for `n < 2^{8}` using LinBox's ``Modular<float>``
 
     These are matrices with integer entries mod ``n`` represented as
     floating-point numbers in a 32-bit word for use with LinBox routines.
-    This allows for ``n`` up to `2^{11}`.  The
-    ``Matrix_modn_dense_double`` class is used for larger moduli.
+    This could allow for ``n`` up to `2^{11}`, but for performance reasons
+    this is limited to ``n`` up to `2^{8}`, and for larger moduli the
+    ``Matrix_modn_dense_double`` class is used.
 
     Routines here are for the most basic access, see the
     ``matrix_modn_dense_template.pxi`` file for higher-level routines.