Revert unjustified latex re-formatting

message_ix/model/MESSAGE/model_solve.gms

@@ -14,7 +14,7 @@ if (%foresight% = 0,
 * This is the standard option; the GAMS global variable ``%foresight%=0`` by default.
 *
 * .. math::
-*    \min_x OBJ = \sum_{y \in Y} OBJ_y(x_y)
+*    \min_x \text{OBJ} = \sum_{y \in Y} \text{OBJ}_y(x_y)
 ***
 
 * reset year in case it was set by MACRO to include the base year before
@@ -75,10 +75,10 @@ else
 * Loop over :math:`\hat{y} \in Y`, solving
 *
 * .. math::
-*     \min_x \ OBJ = \sum_{y \in \hat{Y}(\hat{y})} OBJ_y(x_y) \\
+*     \min_x \ \text{OBJ} = \sum_{y \in \hat{Y}(\hat{y})} \text{OBJ}_y(x_y) \\
 *     \text{s.t. } x_{y'} = x_{y'}^* \quad \forall \ y' < y
 *
-* where :math:`\hat{Y}(\hat{y}) = \{y \in Y | \ |\hat{y}| - |y| < optimization\_horizon \}` and
+* where :math:`\hat{Y}(\hat{y}) = \{y \in Y | \ |\hat{y}| - |y| < \text{optimization_horizon} \}` and
 * :math:`x_{y'}^*` is the optimal value of :math:`x_{y'}` in iteration :math:`|y'|` of the iterative loop.
 *
 * The advantage of this implementation is that there is no need to 'store' the optimal values of all decision