[banjo] Comment typo fixes.

TEST: No behavior change
Change-Id: I28ba22ae00814b5ddb111406f49e618ef338cee3
diff --git a/system/host/banjo/lib/flat_ast.cpp b/system/host/banjo/lib/flat_ast.cpp
index c7c93b6..bec56f8 100644
--- a/system/host/banjo/lib/flat_ast.cpp
+++ b/system/host/banjo/lib/flat_ast.cpp
@@ -1328,7 +1328,7 @@
             auto name_result = method_scope.names.Insert(method.name.data(), method.name);
             if (!name_result.ok())
                 return Fail(method.name,
-                            "Multiple methods with the same name in an interface; last occurance was at " +
+                            "Multiple methods with the same name in an interface; last occurrence was at " +
                                 name_result.previous_occurance().position());
 
             // Add a pointer to this method to the interface_declarations list.
diff --git a/system/host/banjo/lib/source_file.cpp b/system/host/banjo/lib/source_file.cpp
index 872f27b..ac35a52 100644
--- a/system/host/banjo/lib/source_file.cpp
+++ b/system/host/banjo/lib/source_file.cpp
@@ -38,7 +38,7 @@
            "The view is not part of this SourceFile");
 
     // We are looking from the end of the file backwards (hence
-    // crbegin and crend), looking for the the first line (hence
+    // crbegin and crend), looking for the first line (hence
     // upper_bound) to start at or before before the token in
     // question.
     auto is_in_line = [&ptr_less_equal](const StringView& left, const StringView& right) {