Remove ancient .gitignore lines (#4952)

The files referenced here have not existed for some time.

Author: fifieldt

.gitignore

@@ -1,6 +1,4 @@
 .pio
-main/configuration.h
-main/credentials.h
 
 # ignore vscode IDE settings files
 .vscode/*
@@ -32,4 +30,4 @@ release/
 .vscode/extensions.json
 /compile_commands.json
 src/mesh/raspihttp/certificate.pem
-src/mesh/raspihttp/private_key.pem
+src/mesh/raspihttp/private_key.pem