MDL-82086 theme_boost: consistent selector for textarea form controls.

In a similar vein to 31f6039635, we shouldn't assume form controls are
always descendents of `.mform` (e.g. the messaging drawer input).

theme/boost/scss/moodle/forms.scss

@@ -23,9 +23,6 @@
 }
 
 .mform .d-flex {
-    textarea.form-control {
-        width: 100%;
-    }
     .fitem {
         margin: 0.1rem 0.25rem 0.1rem 0 !important; /* stylelint-disable-line declaration-no-important */
     }
@@ -37,9 +34,14 @@
 }
 
 // Override the default bootstrap form-control width.
-.d-flex > .form-control {
-    width: auto;
-    max-width: 100%;
+.d-flex {
+    & > .form-control {
+        width: auto;
+        max-width: 100%;
+    }
+    & > textarea.form-control {
+        width: 100%;
+    }
 }
 
 // Override the default bootstrap custom-select width.

theme/boost/style/moodle.css

@@ -32930,9 +32930,6 @@ body.path-question-type .mform fieldset.hidden {
   margin-bottom: 4px;
 }
 
-.mform .d-flex textarea.form-control {
-  width: 100%;
-}
 .mform .d-flex .fitem {
   margin: 0.1rem 0.25rem 0.1rem 0 !important; /* stylelint-disable-line declaration-no-important */
 }
@@ -32946,6 +32943,9 @@ body.path-question-type .mform fieldset.hidden {
   width: auto;
   max-width: 100%;
 }
+.d-flex > textarea.form-control {
+  width: 100%;
+}
 
 .custom-select {
   width: auto;

theme/classic/style/moodle.css

@@ -32930,9 +32930,6 @@ body.path-question-type .mform fieldset.hidden {
   margin-bottom: 4px;
 }
 
-.mform .d-flex textarea.form-control {
-  width: 100%;
-}
 .mform .d-flex .fitem {
   margin: 0.1rem 0.25rem 0.1rem 0 !important; /* stylelint-disable-line declaration-no-important */
 }
@@ -32946,6 +32943,9 @@ body.path-question-type .mform fieldset.hidden {
   width: auto;
   max-width: 100%;
 }
+.d-flex > textarea.form-control {
+  width: 100%;
+}
 
 .custom-select {
   width: auto;