Fix a few proposal URLs (#7473)

Fixup for #7245

toolchain/check/cpp/import.cpp

@@ -2359,7 +2359,7 @@ static auto LookupBuiltinName(Context& context, SemIR::LocId loc_id,
   const clang::ASTContext& ast_context = context.ast_context();
 
   // List of types based on
-  // https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p005448.md#details
+  // https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p005448-carbon-c-interop-primitive-types.md#details
   auto builtin_type =
       llvm::StringSwitch<clang::QualType>(*name)
           .Case("signed_char", ast_context.SignedCharTy)

toolchain/check/merge.cpp

@@ -484,7 +484,7 @@ static auto CheckRedeclParamSyntax(Context& context,
       // redeclaration matching rule from proposal #3763.
       //
       // Skip difference if it is `Self as` vs. `as` in an `impl` declaration.
-      // https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p003763.md#redeclarations
+      // https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p003763-matching-redeclarations.md#redeclarations
       if (new_node_kind == Parse::NodeKind::ImplDefaultSelfAs &&
           prev_node_kind == Parse::NodeKind::SelfTypeNameExpr &&
           context.parse_tree().node_kind(prev_iter[1]) ==

utils/tree_sitter/grammar.js

@@ -75,7 +75,7 @@ module.exports = grammar({
     comment: ($) => token(seq('//', /.*/)),
 
     // NOTE: this must be before ident rule to increase its priority.
-    // https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p002015.md#syntax
+    // https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p002015-numeric-type-literal-syntax.md#syntax
     numeric_type_literal: ($) => /[iuf][1-9][0-9]*/,
 
     ident: ($) => /[A-Za-z_][A-Za-z0-9_]*/,