lua_api.txt: add missing backticks

doc/lua_api.txt

@@ -1191,7 +1191,7 @@ Look for examples in `games/devtest` or `games/minetest_game`.
  used to compensate for how `glasslike` reduces visual thickness.
 * `torchlike`
  * A single vertical texture.
- * If `paramtype2="[color]wallmounted":
+ * If `paramtype2="[color]wallmounted"`:
  * If placed on top of a node, uses the first texture specified in `tiles`.
  * If placed against the underside of a node, uses the second texture
  specified in `tiles`.
@@ -1203,7 +1203,7 @@ Look for examples in `games/devtest` or `games/minetest_game`.
 * `signlike`
  * A single texture parallel to, and mounted against, the top, underside or
  side of a node.
- * If `paramtype2="[color]wallmounted", it rotates according to `param2`
+ * If `paramtype2="[color]wallmounted"`, it rotates according to `param2`
  * If `paramtype2="none"`, it will always be on the floor.
 * `plantlike`
  * Two vertical and diagonal textures at right-angles to each other.
@@ -4547,7 +4547,7 @@ Callbacks:
  * Called when the object is instantiated.
  * `dtime_s` is the time passed since the object was unloaded, which can be
  used for updating the entity state.
-* `on_deactivate(self, removal)
+* `on_deactivate(self, removal)`
  * Called when the object is about to get removed or unloaded.
  * `removal`: boolean indicating whether the object is about to get removed.
  Calling `object:remove()` on an active object will call this with `removal=true`.