docs: dev-tools: checkpatch.rst: Fix grammar

- s/exists/exist/
- s/maybe/may be/
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240208152039.65293-1-thorsten.blum@toblux.com

Documentation/dev-tools/checkpatch.rst

@@ -168,7 +168,7 @@ Available options:
 
  - --fix
 
-   This is an EXPERIMENTAL feature.  If correctable errors exists, a file
+   This is an EXPERIMENTAL feature.  If correctable errors exist, a file
    <inputfile>.EXPERIMENTAL-checkpatch-fixes is created which has the
    automatically fixable errors corrected.
 
@@ -181,7 +181,7 @@ Available options:
 
  - --ignore-perl-version
 
-   Override checking of perl version.  Runtime errors maybe encountered after
+   Override checking of perl version.  Runtime errors may be encountered after
    enabling this flag if the perl version does not meet the minimum specified.
 
  - --codespell