Lower precision for a number of queries.

These queries are currently run by default, but don't have their results displayed.

Looking through results on LGTM.com, they are either false positives (e.g., `BitwiseSignCheck` which flags many perfectly harmless operations and `CompareIdenticalValues` which mostly flags NaN checks) or harmless results that developers are unlikely to care about (e.g., `EmptyArrayInit` or `MisspelledIdentifier`).

With this PR, the only queries that are still run but not displayed are security queries, where different considerations may apply.

javascript/ql/src/Expressions/BitwiseSignCheck.ql

@@ -6,7 +6,7 @@
  * @id js/bitwise-sign-check
  * @tags reliability
  *       correctness
- * @precision medium
+ * @precision low
  */
 
 import javascript

javascript/ql/src/Expressions/CompareIdenticalValues.ql

@@ -11,7 +11,7 @@
  *       convention
  *       external/cwe/cwe-570
  *       external/cwe/cwe-571
- * @precision medium
+ * @precision low
  */
 
 import Clones

javascript/ql/src/Expressions/MisspelledIdentifier.ql

@@ -6,7 +6,7 @@
  * @id js/misspelled-identifier
  * @tags maintainability
  *       readability
- * @precision high
+ * @precision low
  */
 
 import Misspelling