aja_common: suppres a warning

suppress a warning in AJA headers (as it already is in vcap/aja):
```
/usr/local/include/libajantv2/ajantv2/includes/ntv2formatdescriptor.h:230:113: error: cast from type ‘const void*’ to type ‘UByte*’ {aka ‘unsigned char*’} casts away qualifiers [-Werror=cast-qual]
  230 |         inline UByte *  GetTopVisibleRowAddress (UByte * pInStartAddress) const                         {return (UByte *) GetRowAddress (pInStartAddress, firstActiveLine);}
```

src/aja_common.cpp

@@ -43,6 +43,7 @@
 #include <cinttypes>                 // for PRIx64
 #include <cstdint>                   // for uint64_t
 #include <cstdio>                    // for printf
+#pragma GCC diagnostic ignored "-Wcast-qual"
 #include <ntv2card.h>                // for CNTV2Card
 
 #include "aja_common.hpp"