Fix typos with codespell

Using codespell 1.17.1.

Method:
```
$ cat > ../godot-word-whitelist.txt << EOF
ang
curvelinear
dof
doubleclick
fave
findn
leapyear
lod
merchantibility
nd
numer
ois
ony
que
seeked
synching
te
uint
unselect
webp
EOF

$ codespell -w -q 3 -I ../godot-word-whitelist.txt --skip="./thirdparty,*.po"
$ git diff // undo unwanted changes
```

1 files changed, 1 insertions, 1 deletions

diff --git a/servers/rendering/rasterizer_rd/shaders/volumetric_fog.glsl b/servers/rendering/rasterizer_rd/shaders/volumetric_fog.glsl
index cb19fb0b69..13b162f0c9 100644
--- a/servers/rendering/rasterizer_rd/shaders/volumetric_fog.glsl
+++ b/servers/rendering/rasterizer_rd/shaders/volumetric_fog.glsl
@@ -485,7 +485,7 @@ void main() {
 
 		//get depth at cell pos
 		float z = get_depth_at_pos(fog_cell_size.z, i);
-		//get distance from previos pos
+		//get distance from previous pos
 		float d = abs(prev_z - z);
 		//compute exinction based on beer's
 		float extinction = t * exp(-d * fog.a);