Remove oappend

Remove the large stack buffer as we're just going to copy it in to a
heap buffer anyways.  Later we can refine the length estimation or use a
rope-style dynamic data structure like DynamicBufferList.

wled00/wled.h

@@ -839,10 +839,6 @@ WLED_GLOBAL time_t sunrise _INIT(0);
 WLED_GLOBAL time_t sunset _INIT(0);
 WLED_GLOBAL Toki toki _INIT(Toki());
 
-// Temp buffer
-WLED_GLOBAL char* obuf;
-WLED_GLOBAL uint16_t olen _INIT(0);
-
 // General filesystem
 WLED_GLOBAL size_t fsBytesUsed _INIT(0);
 WLED_GLOBAL size_t fsBytesTotal _INIT(0);