libsysprof-capture: reduce max stack depth

128 is a bit much and can slow us down considerably with user-space stack
traces. This can mess up the tree a bit, but we can alter how we view
things later on if we need to so that it is easier to read.

src/libsysprof-capture/sysprof-capture-writer.c

@@ -78,7 +78,7 @@
 #define DEFAULT_BUFFER_SIZE (_sysprof_getpagesize() * 64L)
 #define INVALID_ADDRESS     (G_GUINT64_CONSTANT(0))
 #define MAX_COUNTERS        ((1 << 24) - 1)
-#define MAX_UNWIND_DEPTH    128
+#define MAX_UNWIND_DEPTH    64
 
 typedef struct
 {