doc: peripherals: i2c: Fix incorrect hyperlink references

This commit fixes incorrect external hyperlink references.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

doc/hardware/peripherals/i2c.rst

@@ -9,7 +9,7 @@ Overview
 .. note::
 
    The terminology used in Zephyr I2C APIs follows that of the
-   `NXP I2C Bus Specification Rev 7.0 <i2c-specification>`_. These changed
+   `NXP I2C Bus Specification Rev 7.0 <i2c-specification_>`_. These changed
    from previous revisions as of its release October 1, 2021.
 
 `I2C <i2c-specification>`_ (Inter-Integrated Circuit, pronounced "eye