Simplify gradient border shader

Cargo.lock

@@ -1390,6 +1390,12 @@ dependencies = [
  "xml-rs",
 ]
 
+[[package]]
+name = "glam"
+version = "0.25.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "151665d9be52f9bb40fc7966565d39666f2d1e69233571b71b87791c7e0528b3"
+
 [[package]]
 name = "glib"
 version = "0.19.0"
@@ -2104,6 +2110,7 @@ dependencies = [
  "directories",
  "futures-util",
  "git-version",
+ "glam",
  "input",
  "keyframe",
  "libc",