Remove assignment from variable declaration section in go.md

Admittedly, I'm at a junior dev level, but I believe the code as written
is syntactically incorrect. I think that the `:` is required for `msg`
to be declared as a variable. I don't believe you can just use the
assignment operator (`=`) to declare `msg` as a variable by assigning it
the value of `"Hello"` in the 'Go!' language like you can in python,
dart, et al.

Go! does have type inference but it must be done with the walrus
operator (`:=`). Line 49 denotes that this is the `Variable Declaration`
section so I believe the `:` preceding the `=` is necessary.

On deeper checking, I think this line should be deleted because it's
syntactically incorrect and the shortcut for variable declaration and
assignment using the walrus operator is already covered below.

go.md

@@ -55,7 +55,6 @@ var msg string = "Hello, world!"
 var x, y int
 var x, y int = 1, 2
 var x, msg = 1, "Hello, world!"
-msg = "Hello"
 ```
 
 #### Declaration list