Tests: widen PNG decoder Valgrind suppression (#1764)

Newer Rust builds may render the Cursor type in the PNG decoder stack as core::io::cursor::Cursor rather than std::io::cursor::Cursor. The existing fuzzy image hash suppression only matched the std::io spelling, so Debian 11 arm64 Valgrind jobs reported a known third-party PNG decoder warning instead of suppressing it.

Use a wildcard for the leading module path so the suppression covers both symbol spellings while still requiring the fuzzy_hash_calculate_image stack.

Author: val-ms

unit_tests/valgrind.supp

@@ -380,7 +380,7 @@
    <image-fuzzy-hash-png-decoder>
    Memcheck:Cond
    ...
-   fun:read_header_info<std::io::cursor::Cursor<&[u8]>>
+   fun:read_header_info<*::io::cursor::Cursor<&[u8]>>
    ...
    fun:fuzzy_hash_calculate_image
    ...