fix unbalanced parentheses for DTRlearn2 (fyi: @julierennes)

Author: zeileis

CausalInference.md

@@ -216,7 +216,7 @@ treatment effect (HTE) estimation.
 
 - *Direct methods* perform a direct classification task: outcome-weighted learning `r pkg("DTRlearn2")`; efficient augmentation/relaxation learning (EARL), residual learning, weighted learning, value-search methods based on Augmented Inverse Probability Weighted Estimators and Inverse Probability Weighted Estimators `r pkg("DynTxRegime")`.
 - *Indirect methods*, which proceed through nuisance estimation to perform Q-learning `r pkg("DTRlearn2")`, `r pkg("DynTxRegime")`, `r pkg("DTRreg")`, Interactive Q-Learning `r pkg("DynTxRegime")` or double robust Q-Learning.
-r pkg("polle") provides a unified framework for learning and evaluating finite stage policies based on observational data with methods such as doubly robust restricted Q-learning, policy tree learning, and outcome weighted learning. Flexible machine learning methods can be used to estimate the nuisance components and valid inference for the policy value is ensured via cross-fitting. The package wraps and extends some functionalities from other packages  `r pkg("DynTxRegime") `,  `r pkg("policytree") `,  `r pkg("grf") `,  `r pkg("DTRlearn2"))`.
+r pkg("polle") provides a unified framework for learning and evaluating finite stage policies based on observational data with methods such as doubly robust restricted Q-learning, policy tree learning, and outcome weighted learning. Flexible machine learning methods can be used to estimate the nuisance components and valid inference for the policy value is ensured via cross-fitting. The package wraps and extends some functionalities from other packages  `r pkg("DynTxRegime") `,  `r pkg("policytree") `,  `r pkg("grf") `,  `r pkg("DTRlearn2")`.
 - *For sequential, multiple assignment, randomized trials (SMART)*
 Set of tools for determining the necessary sample size in order to identify the optimal DTR `r pkg("smartsizer")`. Estimators for general K-stage DTRs from SMARTs `r pkg("DTRlearn2")`.
 - *With variable selection*