Log Message:
py-pdf: update to 3.15.1.

## Version 3.15.1, 2023-08-13

### Performance Improvements (PI)
-  optimize _decode_png_prediction (#2068)

### Bug Fixes (BUG)
-  Fix incorrect tm_matrix in call to visitor_text (#2060)
-  Writing German characters into form fields (#2047)
-  Prevent stall when accessing image in corrupted pdf (#2081)
-  append() fails when articles do not have /T (#2080)

### Robustness (ROB)
-  Cope with xref not followed by separator (#2083)

## Version 3.15.0, 2023-08-06

### New Features (ENH)
-  Add `level` parameter to compress_content_streams (#2044)
-  Process /uniHHHH for text_extract (#2043)

### Bug Fixes (BUG)
-  Fix AnnotationBuilder.link (#2066)
-  JPX image without ColorSpace  (#2062)
-  Added check for field /Info when cloning reader document (#2055)
-  Fix indexed/CMYK images (#2039)

### Maintenance (MAINT)
-  Cryptography as primary dependency (#2053)