Update to FFmpeg n6.1.2 to fix an issue with Rocky Linux 9 and vulkan (AcademySoftwareFoundation#633)

### Fix FFMPEG build error in Rocky Linux 9 CI

### Linked issues
n/a

### Summarize your change.
Updated FFmpeg to version n6.1.2 to fix the issue.

### Describe the reason for the change.
Rocky Linux 9 CI is failing.

### Describe what you have tested and on which operating system.
- [x] Rocky Linux 9

Signed-off-by: Cédrik Fuoco <cedrik.fuoco@autodesk.com>

Author: cedrik-fuoco-adsk

cmake/dependencies/ffmpeg.cmake

@@ -33,17 +33,15 @@ IF(RV_FFMPEG_7)
   )
 ELSEIF(RV_FFMPEG_6)
   SET(_version
-      "n6.1.1"
+      "n6.1.2"
   )
 
   SET(_download_hash
-      "6dfc27fcb6da6f653c6ec025c2cd9b00"
+      "953b858e5be3ab66232bdbb90e42f50d"
   )
 ELSE()
-  # This shouldn't happen, but it could if there are changes the acceptable
-  # versions of FFmpeg in ffmpeg.cmake and this section is not
-  # updated accordingly.
-  message( FATAL_ERROR "The requested version of FFmpeg is not supported." )
+  # This shouldn't happen, but it could if there are changes the acceptable versions of FFmpeg in ffmpeg.cmake and this section is not updated accordingly.
+  MESSAGE(FATAL_ERROR "The requested version of FFmpeg is not supported.")
 ENDIF()
 
 SET(_download_url
@@ -81,7 +79,6 @@ ELSE()
   )
 ENDIF()
 
-
 IF(RV_FFMPEG_7)
   IF(RV_TARGET_DARWIN)
     SET(_ffmpeg_avutil_lib_name
@@ -183,10 +180,8 @@ ELSEIF(RV_FFMPEG_6)
     )
   ENDIF()
 ELSE()
-  # This shouldn't happen. But it could if there are changes the acceptable
-  # versions of FFmpeg in ffmpeg.cmake and this section is not
-  # updated accordingly.
-  message( FATAL_ERROR "The requested version of FFmpeg is not supported." )
+  # This shouldn't happen. But it could if there are changes the acceptable versions of FFmpeg in ffmpeg.cmake and this section is not updated accordingly.
+  MESSAGE(FATAL_ERROR "The requested version of FFmpeg is not supported.")
 ENDIF()
 
 SET(_ffmpeg_libs