Merge pull request #2665 from RuffaloLavoisier/unnecessary

bootflow-2711: fix typo 'unnecessary'

Author: Alasdair Allan

documentation/asciidoc/computers/raspberry-pi/bootflow-2711.adoc

@@ -90,7 +90,7 @@ If `secure-boot` is enabled then `tryboot` mode will cause `tryboot.img` to be l
 
 === TRYBOOT_A_B mode
 If the `tryboot_a_b` property in xref:config_txt.adoc#autoboot-txt[autoboot.txt] is set to `1` then `config.txt` is loaded instead of `tryboot.txt`.
-This is because the `tryboot` switch has already been made at a higher level (the partition) and so it's unecessary to have a `tryboot.txt` file within alternate partition itself.
+This is because the `tryboot` switch has already been made at a higher level (the partition) and so it's unnecessary to have a `tryboot.txt` file within alternate partition itself.
 
 N.B. The `tryboot_a_b` property is implicitly set to `1` when loading files from within a `boot.img` ramdisk.