Typo fixes

Co-authored-by: Cosimo Lupo <[email protected]>

resources/codegen_inputs/layout.rs

@@ -553,12 +553,12 @@ table VariationIndex {
 
 /// A type representing a temporary identifier for a set of variation deltas.
 ///
-/// The final indicies used in the VariationIndex table are not known until
+/// The final indices used in the VariationIndex table are not known until
 /// all deltas have been collected. This variant is used to assign a
 /// temporary identifier during compilation.
 ///
 /// This type is not part of the spec and will never appear in an actual font file.
-/// It is intended to serve as a sentinal value, and will panic when written,
+/// It is intended to serve as a sentinel value, and will panic when written,
 /// ensuring that all VariationIndex tables have been correctly mapped before
 /// the font is compiled.
 #[write_fonts_only]