fix: use relative sqlite3.h in CSQLite module.modulemap for Android cross-compilation

The absolute path '/usr/include/sqlite3.h' does not exist in the Android
NDK sysroot used by the aarch64-unknown-linux-android24 Swift SDK. Using
a relative 'sqlite3.h' lets the compiler find it through the sysroot
include paths automatically during cross-compilation, while still working
on Linux native builds via pkg-config include flags.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: vkuttyp

Sources/CSQLite/module.modulemap

@@ -1,5 +1,5 @@
 module CSQLite [system] {
-    header "/usr/include/sqlite3.h"
+    header "sqlite3.h"
     link "sqlite3"
     export *
 }