Note that case insensitivity is the default

Saying "code search is case-insensitive" then saying "you can do
case-sensitive searches" can seem confusing. Make it less confusing by
noting that case insensitivity is only the default behavior.

content/search-github/github-code-search/understanding-github-code-search-syntax.md

@@ -317,4 +317,4 @@ If code search guesses wrong, you can always get the search you wanted by using
 
 ## Case sensitivity
 
-Code search is case-insensitive. Searching for `True` will include results for _uppercase_ `TRUE` and _lowercase_ `true`. You can do case-sensitive searches by using a regular expression with case insensitivity turned off, for example `(?-i)True`.
+By default, code search is case-insensitive. Searching for `True` will include results for _uppercase_ `TRUE` and _lowercase_ `true`. You can do case-sensitive searches by using a regular expression with case insensitivity turned off, for example `(?-i)True`.